© 1995 American Heart Association, Inc.
Articles |
Brain ‘Ouabain’ Mediates Sympathetic Hyperactivity in Congestive Heart Failure
From the Hypertension Unit, Division of Cardiology, University of Ottawa (Canada) Heart Institute.
Correspondence to Frans H.H. Leenen, MD, PhD, FRCPC, Hypertension Unit, H360, University of Ottawa Heart Institute, 1053 Carling Ave, Ottawa, Ontario, Canada, K1Y 4E9. E-mail fleenen@ohi-net.heartinst.on.ca.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Abstract In congestive heart failure (CHF), endogenous compounds with ouabainlike activity (OLA) may contribute to the maintenance of the circulatory homeostasis by peripheral as well as central effects. In the present study, we assessed changes in peripheral (plasma and left ventricle) and central (pituitary, hypothalamus, pons, and cortex) OLA in two animal models of CHF and determined whether brain OLA mediates sympathetic hyperactivity in CHF. Cardiomyopathic hamsters with their controls were studied at 9 months of age for tissue OLA. Rats were studied 4 weeks after acute coronary artery ligation for tissue OLA and sympathetic activity. In both models, left ventricular end-diastolic pressure was markedly increased. CHF was associated with significant increases in both plasma and tissue OLA in both models. In the brain, the most marked (twofold to threefold) increases occurred in the hypothalamus. In vitro, all OLA measured could be blocked by antibody Fab fragments (Digibind). Conscious rats with CHF showed elevated plasma catecholamines and enhanced responses of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) to air stress and to intracerebroventricular (ICV) injection of the
2-adrenergic receptor agonist guanabenz compared
with sham-operated rats. ICV administration of the Fab fragments
did not change resting RSNA or responses to air stress at 1 hour.
However, 18 hours after injection of the Fab fragments, resting RSNA
levels had significantly decreased compared with the control values,
and plasma catecholamine levels had decreased to control
values. Moreover, the magnitudes of the increases or decreases in MAP,
HR, and RSNA to air stress or ICV guanabenz had markedly decreased as
well and were now similar to those observed in sham-operated
control animals. The present results show that the development of
CHF in two animal models is associated with marked increases in both
peripheral and brain OLA. Brain OLA appears to mediate the
increase in resting sympathetic tone and enhanced
sympathoexcitatory responses to stress.
Key Words: ouabain • brain • heart • heart failure • sympathetic activity
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
For several decades, a number of laboratories have been pursuing the identity of endogenous compounds with digitalis-like activity. In recent years, evidence has been increasing that this inhibitor of the Na+,K+-ATPase enzyme may be a steroid closely related to ouabain.1 2 3 Regarding the possible (patho)physiological role of such compounds with OLA, most studies have focused on their effects on kidneys, arteries, and the heart.4 5 In recent years, our research has clearly established a major role for compounds with OLA in the central regulation of sympathetic outflow and BP: in rat models of genetic hypertension, high sodium intake increases brain OLA,6 7 and antibody Fab fragments (Digibind) with high affinity for ouabain and brain OLA administered in the left lateral cerebral ventricle prevent/reverse the sympathoexcitatory and pressor effects of high sodium.8 9
In congestive heart failure, sympathetic activity increases in parallel with the impairment of cardiac performance10 11 12 and may contribute to the progression of heart failure.13 The actual mechanisms responsible for the increase in sympathetic tone have not yet been clearly defined. Ferguson14 and Floras15 have suggested that impairment of cardiopulmonary and arterial baroreflex sensory mechanisms plays a major role in the sympathoexcitation with heart failure. In contrast, Kaye et al16 state that "the fundamental links between the hemodynamic afferent stimulus, central neural processing and sustained elevation of peripheral sympathetic outflow remain unclear." Although multiple receptor populations are likely involved, studies in both animals and humans do indicate that increases in LV filling pressures and atrial or pulmonary arterial pressures appear to represent the primary stimulus for sympathetic hyperactivity in heart failure.10 16 17 Since this also represents a stimulus for release of endogenous OLA,18 we postulate that chronic increases in filling pressures as observed in heart failure not only increase peripheral OLA19 but also increase brain OLA and that the latter leads to increased sympathetic outflow. As a first step in assessing this hypothesis, we measured brain versus peripheral OLA in two animal models of heart failure, ie, cardiomyopathic hamsters20 21 and rats with myocardial infarction induced by acute coronary artery ligation.22 The results show that in these two animal models, heart failure is indeed associated with major increases in brain OLA and that the enzyme-inhibitory activity of the latter can be blocked by Digibind. To assess the actual pathophysiological role of brain OLA in heart failure, we evaluated whether blockade of brain OLA by the Fab fragments normalizes sympathetic hyperactivity in rats with CHF. These results indicate that brain OLA indeed appears to mediate the increased sympathetic activity associated with CHF.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Animal Models of CHF
Hamsters
Eight male hamsters at 270 to 280 days of age (CHF 147) and eight age-matched control male hamsters (CHF 148) were obtained from the Canadian Hybrid Farms, Kings County, Nova Scotia, Canada. The hamsters were housed individually on a 12-hour light/dark schedule and provided with normal rat chow and tap water. They were allowed to adapt to the new surroundings for 7 to 10 days.
Rats
Male normotensive Wistar rats weighing 250 to 300 g were
obtained from Charles Rivers Breeding Laboratories, Montreal, Quebec,
Canada. The rats were fed standard rat chow and water ad libitum. After
a 5-day acclimatization period, acute coronary ligation was
performed as described previously.23 Briefly, rats were
anesthetized with 1.0% halothane in oxygen/nitrous oxide,
intubated, and connected to a respirator (Harvard Rodent Ventilator,
model 683). After opening the thorax at the fourth or fifth left
intercostal space, the left coronary artery was ligated at 2 to
3 mm from its origin with a 6-0 silk suture attached to an atraumatic
needle (K801H, Ethicon Inc). The rats were followed up for 4 weeks. In
the first experiment, 8 rats with CHF were studied, whereas rats that
underwent sham surgery (n=4) and those (n=2) showing no infarction at
postmortem were pooled as the control group. In the second experiment,
14 rats with CHF were studied (2 of these died during surgery) along
with 6 sham-operated rats.
Experimental Protocol I
Hemodynamic Assessment and Sampling for
OLA
Animals were subjected to 1.0% halothane in oxygen/nitrous
oxide anesthesia, and a polyethylene catheter (PE-10 for
hamsters and PE-50 for rats) filled with heparinized saline (100 U
heparin per milliliter) was placed in the LV via the right carotid
artery. After a 3-hour recovery period, LVPSP and LVEDP were measured
in resting, unrestrained, conscious animals.24
At the conclusion of hemodynamic measurements, in rats 1 mL of blood was collected through the LV catheter, and in hamsters under halothane anesthesia 0.5 mL of blood was obtained by puncturing the heart with a 23-gauge needle. The blood was put into a prechilled tube containing 20 µL of 0.0026 mol/L EDTA. The heart was removed, the LV and RV were weighed, and infarct size was determined according to Chien et al.25 For this, four or five incisions were made in the LV from base to apex, and the LV tissue was pressed flat. The circumferences of the entire flat LV and the infarcted area were outlined on a clean overhead plastic sheet. The outlined area of the whole LV was cut off and weighed, and then the infarct area was cut off and weighed. The infarct size was expressed as the ratio of these two weights. The normal LV tissue was collected for OLA assay. The brain and pituitary from each animal were also sampled. Plasma and tissue samples (wrapped in aluminum foil) were stored at -80°C. The cortical, hypothalamic, and pons tissue were obtained by dissection of the brain at 4°C according to Glowinski and Iversen.26 As landmarks for the hypothalamus, the optic chiasma and anterior commissure were used as the frontal limit, and the line between the posterior hypothalamus and mammillary bodies was used as the caudal limit. The pons was obtained from the rhombencephalon by removing the cerebellum and medulla oblongata.
Assay for OLA
Plasma and tissue OLA was extracted, and the
Na+,K+-ATPase inhibitory
activity was determined as described previously.6 7
Briefly, tissues were homogenized and deproteinized. After
centrifugation, the supernatant was run through a
Sep-Pak C18 column (Waters-Millipore). The OLA was eluted
from the column with 60% acetonitrile. Plasma was deproteinized by
adding 6% trichloroacetic acid (1:1 [vol/vol]). After mixing
for 2 minutes, the plasma was left at 4°C for 30 minutes and then
centrifuged at 15 000g for 10 minutes at 4°C. The
supernatant was transferred to a glass tube, and the acid was removed
by extraction with water-saturated ether (ether/plasma, 5:1
[vol/vol]) until the pH of the plasma was between 5.0 and 6.0.
Quantification of OLA was performed by measuring 32P
liberated from [
-32P]ATP (New England Nuclear) that
was hydrolyzed by ouabain-sensitive
Na+,K+-ATPase prepared from dog kidneys
(Sigma Chemical Co) with or without the presence of specific amounts of
ouabain or tissue/plasma extract. OLA is expressed as nanograms of
ouabain equivalents per milliliter plasma and micrograms of ouabain
equivalents per gram tissue.
Experimental Protocol II
In rats, ICV cannulas were placed at 2.5 to 3 weeks after the
coronary artery ligation, as described
previously.27 Briefly, with the animals under sodium
pentobarbital anesthesia a 23-gauge, 14-mm-long
stainless steel tubing was implanted and fixed above the left lateral
cerebral ventricle as a guide cannula (0.5 mm posterior and 1.4 mm
lateral to bregma and 2.8 mm deep from dura). Early in the morning
approximately 3.5 to 4 weeks after the coronary artery
ligation, animals were placed under halothane anesthesia,
and catheters filled with heparinized saline were placed in the right
femoral artery and jugular vein. After intravenous
injection of methohexital sodium (Brevital, 30 mg/kg supplemented with
10 mg/kg as needed, Eli Lilly Canada Inc), a pair of platinum
electrodes (Leico Industries) was placed around the left renal nerve
through a flank incision.27 The nerve and the electrodes
were fixed to each other with silicone rubber (SilGil 604, Wacker). The
electrodes and catheters were tunneled subcutaneously to the back of
the neck, and the rats were then allowed to recover from the
anesthesia and surgery.
Four to 5 hours after the surgery, each rat was placed in a small cage that permitted movement back and forth. The intraarterial catheter was connected to a transducer, and BP and HR were recorded through a polygraph (model 7E, Grass Instrument Co) and a Grass 7P44 tachograph. The electrodes were linked to a Grass P511 bandpass amplifier, and RSNA (spikes per second) was counted by a nerve traffic analyzer (model 706C, University of Iowa Bioengineering). For repeated measurements, the window setting for recording of RSNA remained the same for each rat. At the end of an experiment, the rats were killed, and the background noise of the RSNA recording was measured by directly recording the activity 20 minutes after the animal was killed. The actual RSNA was determined by subtracting noise from total activity. Data were digitized through a microcomputer.
A 26-gauge L-shaped stainless steel needle was used for ICV injection. The shorter arm of the needle was inserted into the guide cannula so that its tip protruded 0.8 to 1.0 mm from the tip of the guide cannula into the lateral ventricle. The longer arm was outside the guide cannula and connected to a Hamilton microsyringe (volume, 10 µL) via a polyethylene catheter (PE-10 fused to PE-50).
Assessment of Sympathetic Responsiveness
After a 30-minute stabilization period, basal MAP, HR, and RSNA
were recorded. Standardized mental stress27 was then
provided twice at a 5-minute interval by blowing the face of the rat
with a jet of air (1 to 1.5 PSL) from a plastic tube located 3 cm in
front of the animal. Changes in MAP, HR, and RSNA were recorded
along with the average of the responses to the two air stresses in each
rat used. After a 15-minute rest, the 2-adrenoceptor
agonist guanabenz (Sigma) dissolved in saline was injected ICV at doses
of 25 and 75 µg per 1 to 3 µL at a 10-minute interval. Resting and
peak changes in MAP, HR, and RSNA were recorded.
After a 20-minute rest, rats were injected with either Digibind or
aspecific 
-globulins, both at 132 µg/6 µL ICV.8
One hour after this injection, basal MAP, HR, and RSNA were again
recorded, followed by assessment of responses to air stress.
Subsequently, the rats were disconnected from the polygraph and
amplifier, and the catheters were sealed with a stylet after having
been filled with heparinized saline. The rats were returned to their
regular cages with free access to food and water. At 18 hours after the
ICV injection of the Fab fragments or -globulins, each rat was
returned to the small cage. After a 30-minute rest, resting MAP, HR,
and RSNA were recorded, followed by measurement of the responses to
air stress and 75 µg ICV guanabenz. Fig 1
shows
typical tracings of BP, RSNA, and HR responses induced by air stress
and ICV guanabenz in a rat with CHF before (Fig 1A) and 18 hours after
(Fig 1B) ICV injection of the Fab fragments. Approximately 20 hours
after the ICV injection of either the Fab fragments or
-globulins (
30 minutes after the effects of ICV guanabenz had
disappeared), a 2-mL blood sample was obtained from the resting,
undisturbed rats. Plasma catecholamine levels were
determined by radioenzymatic assay.28 Other biochemical
parameters (Table 5) were analyzed on a Hitachi 737
multichannel analyzer (Boehringer Mannheim Canada) by
standard hospital procedures.
|
|
At the end of the experiment, after recording background noise of RSNA, methylene blue was injected ICV for assessment of the accuracy of the ICV cannulation, and the hearts were removed for assessment of LV and RV weight and infarct size.
Data Analysis
RSNA responses to Fab fragments or -globulins, air
stress, and guanabenz were expressed as percent changes from resting
levels. Peak responses to air stress and ICV guanabenz were calculated
for statistical analysis. In experimental protocol I,
comparisons between the two groups in each species were performed by
unpaired t test. In experimental protocol II, two-way
ANOVA for repeated measurements was performed by using SAS
software (SAS Institute Inc). When F ratios were significant, a Duncan
multirange test was followed. Statistical significance was defined as
P<.05.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Experimental Protocol I
Resting Hemodynamics
Resting hemodynamics for hamsters and rats are shown in Table 1
. In cardiomyopathic
hamsters, LVPSP was significantly decreased, and LVEDP increased. In
rats, a similar pattern, ie, a significant decrease in LVPSP and a
marked increase in LVEDP, was seen. Neither the
cardiomyopathic hamsters nor the rats with myocardial
infarction showed overt clinical symptoms of heart failure.
|
Ventricular Weights
Ventricular weights for hamsters and rats are also
shown in Table 1
. In cardiomyopathic hamsters, both LV
and RV weight were significantly increased. Despite marked thinning of
the infarcted area, LV weight was significantly higher in rats with
myocardial infarction than in control rats. RV weight was also
significantly increased.
Plasma and Tissue OLA
Plasma and tissue OLA values are given for rats and hamsters in
Table 2. Heart failure was associated with significant
increases in plasma OLA in both models: by 50% in
cardiomyopathic hamsters and by 100% in rats with
myocardial infarction. In contrast, LV OLA increased more markedly in
hamsters versus rats. In the brain of both species, very high
concentrations of OLA were noted in the pituitary, whereas
concentrations in the hypothalamus, pons, and cortex were 10- to
20-fold less compared with the pituitary. Heart failure caused
significant increases in brain OLA. As for the LV, the clearest
increases occurred in the hamsters; eg, there was a >100% increase in
OLA in the pituitary of hamsters versus a 50% increase in the
pituitary of rats. In the other brain tissues, the most marked (twofold
to threefold) increases occurred in the hypothalamus, and less marked
(50%) increases occurred in the pons and cortex.
|
Table 3 shows two standard curves for ouabain and
the effects of the antibody Fab fragments on the inhibition of the
enzyme caused by ouabain or by OLA from different tissues. The Fab
fragments prevented the inhibitory effects of ouabain in a
dose-related fashion, with 6 µg of the Fab fragments blocking
40 ng of ouabain. The inhibitory action of the tissue
extracts containing OLA was also blocked by the Fab fragments in a
dose-related fashion and with a similar potency. Moreover, all OLA
could be blocked by the Fab fragments both in the LV and in the brain
of rats and hamsters with or without CHF.
|
Experimental Protocol II
Resting MAP, HR, and RSNA
Resting MAP, HR, and RSNA are shown in Table 4.
Basal MAP and HR were similar for the sham-operated and CHF groups.
Administration of Fab fragments or -globulins ICV did not result
in changes in MAP or HR. In control rats, RSNA showed a modest decrease
with time. This decrease was significantly larger in CHF rats treated
with Fab fragments. In CHF rats treated with ICV -globulins,
both plasma norepinephrine and epinephrine levels
were clearly elevated compared with levels in sham-operated control
rats. In contrast, in CHF rats treated with ICV Fab fragments, plasma
catecholamine levels were similar to the levels in the
sham-operated group (Fig 2).
|
|
Responses to Air Stress
Responses to air stress are shown in Fig 3. Air
stress elicited rapid increases in MAP, HR, and RSNA. All these
responses were significantly larger (two to three times) in CHF rats
compared with sham-operated rats. At 1 hour after administration of
Fab fragments or -globulin, responses of similar magnitude were
obtained (data not shown). Similar responses were also noted at 18
hours in the sham-operated group and in the CHF group treated with
-globulins, with persistence of the enhancement found in the
latter group. In contrast, the CHF rats treated with Fab fragments no
longer showed enhanced responses and, at this point, showed responses
similar to the sham-operated group.
|
Responses to ICV Guanabenz
Responses to guanabenz are shown in Fig 4. ICV
guanabenz caused dose-related decreases in MAP, HR, and RSNA
(responses to 25 µg being about one third of those to 75 µg; data
not shown). All these responses were significantly greater
(approximately twofold) in the CHF rats compared with the
sham-operated rats. After 18 hours, responses in the
sham-operated group were unchanged. Similarly, in the CHF rats
treated with -globulin, responses remained significantly larger.
In contrast, 18 hours after the administration of Fab fragments, CHF
rats no longer showed enhanced responses, and responses were now
similar to those of sham-operated rats.
|
Renal and Hepatic Function
Global assessment of renal and hepatic function showed no
difference between rats with CHF and sham-operated control rats
(Table 5).
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The present study provides several new findings pointing to the new concept that brain OLA mediates the sympathetic hyperactivity in CHF. First, the development of CHF in both rats and hamsters is associated with marked increases in both peripheral and brain OLA. The magnitude of these increases is at least as large as that observed in Dahl salt-sensitive rats and SHR on high sodium intake.6 7 Second, rats with CHF show clear evidence for decreased sympathoinhibition and increased sympathoexcitation. Third, blockade of brain OLA in rats with CHF normalizes plasma catecholamines, decreases resting RSNA, and normalizes sympathoinhibitory and sympathoexcitatory responses.
CHF and OLA
As far as we are aware, no previous studies have evaluated
circulating or tissue OLA in animals with heart failure. In humans,
Gottlieb et al19 reported significant inverse relations
between plasma ouabain concentrations and cardiac index and BP in
patients with CHF. More recently, Doris et al29 did find
ouabain immunoreactive material but no authentic ouabain in the plasma
of patients with CHF. Other studies also failed to identify authentic
plant ouabain in the plasma of humans.1 30 Thus, the
actual identity of the compound(s) with OLA is not yet established, and
caution should be used in the interpretation of negative results
obtained with assays using antibodies highly specific against plant
ouabain.31 In the present study, OLA was quantified by
an assay for Na+,K+-ATPase
inhibitory activity. This assay is sensitive but not
specific. However, all activity measured with this assay was chemically
closely related to the cardiac glycosides, since Digibind blocked all
activity in both strains of animals with or without CHF. Using this
approach, we have shown increases in OLA by 50% to 100% both
peripherally (plasma and LV) and centrally (pituitary,
hypothalamus, pons, and cortex). In both species, central changes were
most marked in the hypothalamus. Specific hemodynamic
or other consequences of LV dysfunction that cause the increase in
central and peripheral OLA cannot be addressed from the
present study, nor can the actual production site(s), ie,
central and/or peripheral.32
The (patho)physiological importance of increases in peripheral or central OLA in CHF has so far not been assessed. Peripheral OLA may lead via inhibition of the Na+-K+ pump to, for example, improved myocardial inotropic responses,33 natriuresis,34 and maintenance of BP by causing vasoconstriction.4 In addition, the decrease in baroreceptor afferent nerve activity as shown in rats35 36 or dogs37 38 with CHF may be restored by peripheral OLA toward normal.38 However, the extent to which increases in peripheral OLA in CHF or salt-sensitive hypertension8 9 are sufficiently high to cause such effects has not yet been evaluated. Centrally, ouabain and compounds with OLA cause dose-related sympathoexcitatory responses (eg, see Reference 2727 ). Changes in brain OLA in CHF can be expected to be of pathophysiological relevance, since in both Dahl salt-sensitive rats and SHR blockade of the effects of similar increases in brain OLA prevents the sympathoexcitatory and pressor responses to high dietary sodium intake.8 9
CHF and Sympathetic Activity
In humans,13 dogs,17
rats,38 and hamsters,21 CHF is associated
with chronic and progressive sympathetic hyperactivity, and the latter
may account at least partially for disease progression in
CHF.13 Studies in both animals and humans suggest that
impairment of cardiopulmonary and arterial
baroreflex sensory mechanisms are important pathogenetic mechanisms
underlying the sympathoexcitation in CHF.14 15 35 36 37 38 In
addition, central mechanisms appear to contribute to sympathoexcitation
in humans16 and hamsters.39 40 In rats with
CHF, basal RSNA was elevated as evaluated by the cycle activity from
multifiber recordings.41 Whereas baroreflex
control of RSNA was attenuated, responses of RSNA to noxious
stimulation were enhanced.41 In the present study, we
evaluated activity in sympathoexcitatory
pathways by assessing responses to air stress and activity in
sympathoinhibitory pathways by assessing responses to
the 2-adrenoceptor agonist guanabenz ICV. Decreased
sympathoinhibition is associated with enhanced
sympathoinhibitory responses to guanabenz, because of
upregulation and/or decreased receptor occupancy of
2-adrenoceptors in the anterior
hypothalamus.42 43 Our results show significantly (twofold
to threefold) enhanced responses of BP, HR, and RSNA to both air stress
and ICV guanabenz. These findings are consistent with less
sympathoinhibition and enhanced sympathoexcitation. Such a pattern of
changes in the central nervous system likely contributes to a major
extent to the peripheral sympathetic hyperactivity in
CHF.
Central OLA: Mediator of the Sympathetic Hyperactivity in
CHF?
The pattern of changes described in the previous paragraph is
rather similar to the changes that were induced by high dietary sodium
in Dahl salt-sensitive rats and SHR and that can be
prevented/reversed by blockade of brain OLA using chronic ICV infusion
of Digibind.8 9 44 45 Therefore, we hypothesized that of
the several putative effects of endogenous OLA in CHF, its
effects on the brain leading to enhanced sympathetic outflow are the
most important. This hypothesis can be tested by blockade of brain OLA
by using Digibind, as shown in Table 3. In Dahl salt-sensitive
rats, it requires several hours before the effects of the ICV Fab
fragments on sympathetic activity and BP become apparent,8
consistent with findings of Balzan et al,46 who
showed that the reversal by the Fab fragments of an established binding
of ouabain to the receptors required 12 hours. In the present
study, 1 hour after administration of the Fab fragments, responses to
air stress remained enhanced in rats with CHF. However, after 18 hours,
all (ie, BP, HR, and RSNA) responses in rats with CHF to both air
stress and ICV guanabenz had fully returned to the magnitude of
responses in sham-operated rats. Responses in control rats with CHF
remained enhanced. Moreover, the Fab fragments normalized both plasma
norepinephrine and epinephrine levels in rats with
CHF and decreased resting RSNA in rats with CHF by nearly 40% (in
control rats by only 15%). Altogether, these results appear to
indicate that LV dysfunction causes an increase in brain OLA and that
the latter increases resting sympathetic activity (including RSNA) as
well as increases sympathoexcitatory responses
to stress, with enhanced responses of BP and HR as well as RSNA.
Surprisingly, the resting BP of rats with CHF was not affected by the Fab fragments. In the absence of data on cardiac output and LV filling pressures, these findings are difficult to interpret, but they may point to activation of compensatory mechanisms, such as vasopressin or renin, maintaining BP. The extent to which peripheral effects of centrally administered Fab fragments developed over the 18 hours of follow-up cannot be assessed from our study design.
Conclusion
The present results strongly support the major novel concept
that brain OLA leads to sympathetic hyperactivity in CHF. Chronic
blockade of brain OLA also provides a new approach in the modulation of
sympathetic tone in CHF and its consequences for the
maintenance of circulatory homeostasis in CHF and for disease
progression.
|
Selected Abbreviations and Acronyms |
|---|
|
|
Acknowledgments |
|---|
This study was supported by operating grants from the Medical Research Council of Canada and Burroughs Wellcome Inc, Canada. Dr Leenen is a Career Investigator of the Heart and Stroke Foundation of Ontario. Digibind was a generous gift from Burroughs Wellcome Inc, Canada. The cardiomyopathic hamsters were generously donated by the Canadian Hybrid Farms.
Received March 29, 1995; accepted July 7, 1995.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1. Gomez-Sanchez EP, Froecking MF, Sellers D, Blankenship MS, Gomez-Sanchez CE. Is the circulating ouabain-like compound ouabain? Am J Hypertens.. 1994;7:647-650. [Medline] [Order article via Infotrieve]
2.
Hamlyn JM, Blaustein MP, Bova S, DuCharme DW, Harris
DW, Mandel F, Mathews WR, Ludens JH. Identification and
characterization of a ouabain-like compound from human
plasma. Proc Natl Acad Sci U S A.. 1991;88:6259-6263.
3.
Tymiak AA, Norman JA, Bolgar M, DiDonato GC, Lee H,
Parker WL, Lo L, Berova N, Nakanishi K, Haber E, Haupert GT.
Physicochemical characterization of a ouabain isomer isolated
from bovine hypothalamus. Proc Natl Acad Sci
U S A.. 1993;90:8189-8193.
4. Blaustein MP, Hamlyn JM. Pathogenesis of essential hypertension: a link between dietary salt and high blood pressure. Hypertension. 1991;18(suppl III):III-184-III-195.
5. Kramer HJ, Meyer-Lehnert H, Michel H, Predel HG. Endogenous natriuretic and ouabain-like factors: their roles in body fluid volume and blood pressure regulation. Am J Hypertens.. 1991;4:81-89. [Medline] [Order article via Infotrieve]
6. Leenen FHH, Harmsen E, Yu H, Ou C. Effects of dietary sodium on central and peripheral ouabain-like activity in spontaneously hypertensive rats. Am J Physiol. 1993;264(Heart Circ Physiol 33):H2051-H2055.
7. Leenen FHH, Harmsen E, Yu H. Dietary sodium and central vs. peripheral ouabain-like activity in Dahl salt-sensitive vs. salt-resistant rats. Am J Physiol. 1994;267(Heart Circ Physiol 36):H91916-H1920.
8.
Huang BS, Leenen FHH. Brain ‘ouabain’
mediates the sympathoexcitatory and
hypertensive effects of high sodium intake in Dahl salt-sensitive
rats. Circ Res.. 1994;74:586-595.
9. Huang BS, Leenen FHH. Brain ‘ouabain’ mediates Na+-induced increase in BP and blunted arterial baroreflex function in spontaneously hypertensive rats. Hypertension.. 1994;24:377. Abstract.
10. Ferguson DW, Berg WJ, Sanders JS. Clinical and hemodynamic correlates of sympathetic nerve activity in normal humans and patients with heart failure: evidence from direct microneurographic recordings. J Am Coll Cardiol.. 1990;16:1125-1134. [Abstract]
11.
Leimbach WN, Wallin BG, Victor GR, Aylward PE, Sundlof
G, Mark AL. Direct evidence from intraneural recordings
of increased central sympathetic outflow in patients with heart
failure. Circulation. 1986;73:913-919.
12.
Meredith IT, Eisenhofer G, Lambert GW, Dewar EM,
Jennings GL, Esler MD. Cardiac sympathetic nervous activity in
congestive heart failure: evidence for increased neuronal
norepinephrine release and preserved neuronal
uptake. Circulation. 1993;88:136-145.
13. Packer M. The neurohormonal hypothesis: a theory to explain the mechanism of disease progression in heart failure. J Am Coll Cardiol.. 1992;20:248-254. [Abstract]
14. Ferguson DW. Sympathetic mechanisms in heart failure: pathophysiological and pharmacological implications. Circulation. 1993;87(suppl VII):VII-68-VII-75.
15. Floras JS. Clinical aspects of sympathetic activation and parasympathetic withdrawal in heart failure. J Am Coll Cardiol. 1993;22(suppl A):72A-84A.
16. Kaye DM, Lambert GW, Lefkovits J, Morris M, Jennings G, Esler MD. Neurochemical evidence of cardiac sympathetic activation and increased central nervous system norepinephrine turnover in severe congestive heart failure. J Am Coll Cardiol.. 1994;23:570-578. [Abstract]
17. Moe GW, Stopps TP, Angus C, Forster C, De Bold AJ, Armstrong PW. Alterations in serum sodium in relation to atrial natriuretic factor and other neuroendocrine variables in experimental pacing-induced heart failure. J Am Coll Cardiol.. 1989;13:173-179. [Abstract]
18. Pamnani MB, Burris JF, Jemionek JF, Hout SJ, Price M, Freis ED. Humoral Na+-K+ pump inhibitory activity in essential hypertension and normotensive subjects after acute volume expansion. Am J Hypertens.. 1989;2:524-531. [Medline] [Order article via Infotrieve]
19.
Gottlieb SS, Rogowski AC, Weinberg M, Krichten CM,
Hamilton BP, Hamlyn JM. Elevated concentrations of
endogenous ouabain in patients with congestive heart
failure. Circulation. 1992;86:420-425.
20.
Kagiya T, Hori M, Iwakura K, Iwai K, Watanabe Y, Uchida
S, Yoshida H, Kitabatake A, Inoue M, Kamada T. Role of increased
1-adrenergic activity in cardiomyopathic
Syrian hamster. Am J Physiol. 1991;260(Heart
Circ Physiol 29):H80-H88.
21.
Sole MJ, Lo CM, Laird CW, Sonnenblick EH, Wurtman RJ.
Norepinephrine turnover in the heart and spleen of
the cardiomyopathic Syrian hamster. Circ
Res.. 1975;37:855-862.
22. Pfeffer JM, Pfeffer MA, Fletcher PJ, Braunwald E. Progressive ventricular remodeling in rat with myocardial infarction. Am J Physiol. 1991;260(Heart Circ Physiol 29):H1406-H1414.
23.
Pfeffer MA, Pfeffer JM, Fishbein MC, Fletcher JP,
Spadaro J, Kloner RA, Braunwald E. Myocardial infarct size and
ventricular function in rats. Circ Res.. 1979;44:503-512.
24. Yuan B, Leenen FHH. Chronic arterial vasodilation, central hemodynamics, and cardiac hypertrophy in spontaneously hypertensive rats. J Cardiovasc Pharmacol.. 1992;19:922-928. [Medline] [Order article via Infotrieve]
25.
Chien YW, Barbee RW, MacPhee AA, Frohlich ED, Trippodo
NC. Increased ANF secretion after volume expansion is preserved
in rats with heart failure. Am J Physiol.. 1988;254:R185-R191.
26. Glowinski J, Iversen LL. Regional studies of catecholamines in the rat brain, I: the disposition of [3H]norepinephrine, [3H]dopamine and [3H]dopa in various regions of the brain. J Neurochem.. 1966;13:655-669. [Medline] [Order article via Infotrieve]
27.
Huang BS, Harmsen E, Yu H, Leenen FHH. Brain
ouabain-like activity and the
sympathoexcitatory and pressor effects of
central sodium in rats. Circ Res.. 1992;71:1059-1066.
28. Sole MJ, Hussain MN. A simple specific radioenzymatic assay for the simultaneous measurement of picogram quantities of norepinephrine and dopamine in plasma and tissues. Biol Med.. 1977;18:301-307.
29.
Doris PA, Jenkins LA, Stocco DM. Is ouabain an
authentic endogenous mammalian substance derived from the
adrenal? Hypertension.. 1994;23:632-638.
30.
Lewis LK, Yandle TG, Lewis JG, Richards AM, Pidgeon GB,
Kaaja RJ, Nicholls MG. Ouabain is not detectable in human
plasma. Hypertension.. 1994;24:549-555.
31. Hilton PJ, Hilton MJ, Forni L. Poisons and regulators of the sodium pump. Hypertension.. 1995;25:460.
32.
Leenen FHH, Harmsen E, Yu H, Yuan B. Dietary
sodium stimulates ouabain-like activity in adrenalectomized
spontaneously hypertensive rats. Am J Physiol.. 1993;265:H421-H424.
33.
Ochs HR, Vatner SF, Smith TW. Reversal of
inotropic effects of digoxin by specific antibody and their Fab
fragments in the conscious dog. J Pharmacol Exp
Ther.. 1978;207:64-71.
34.
de Wardener HE. Kidney, salt intake, and
Na+,K+-ATPase inhibitors in
hypertension: 1990 Corcoran Lecture. Hypertension.. 1991;17:830-836.
35.
Jung R, Dibner-Dunlap ME, Gilles MA, Thames MD.
Cardiorespiratory reflex control in rats with left
ventricular dysfunction. Am J Physiol.. 1995;268:H218-H225.
36.
DiBona GF, Sawin LL. Reflex regulation of renal
nerve activity in cardiac failure. Am J Physiol.. 1994;266:R27-R39.
37.
Dibner-Dunlap ME, Thames MD. Baroreflex control
of renal sympathetic nerve activity is preserved in heart failure
despite reduced arterial baroreceptor sensitivity.
Circ Res.. 1989;65:1526-1535.
38.
Wang W, Chen JS, Zucker IH. Carotid sinus
baroreceptor sensitivity in experimental heart failure.
Circulation. 1990;81:1959-1966.
39. Sole MJ, Benedict CR, Versteeg DHG, de Kloet ER. Digitoxin therapy partially restores cardiac catecholamine and brain serotonin metabolism in congestive heart failure. J Mol Cell Cardiol.. 1985;17:1055-1063.[Medline] [Order article via Infotrieve]
40.
Sole MJ, Shum A, Van Loon GR. Alterations in
brain serotonin during congestive heart failure in the
cardiomyopathic Syrian hamster.
Cardiovasc Res.. 1978;12:373-375.
41. Feng QP, Carlsson S, Thorén P, Hedner T. Characteristics of renal sympathetic nerve activity in experimental congestive heart failure in the rat. Acta Physiol Scand.. 1994;150:259-266. [Medline] [Order article via Infotrieve]
42. Oparil S, Chen Y-F, Meng Q, Yang RH, Jim H, Wyss JM. The neural basis of salt sensitivity in the rats: altered hypothalamic function. Am J Med Sci.. 1988;295:360-362. [Medline] [Order article via Infotrieve]
43. Wyss JM, Yang R, Jin H, Oparil S. Hypothalamic microinjection of alpha2-adrenergic receptor agonists causes greater sympathoinhibition in spontaneously hypertensive rats on high NaCl diets. J Hypertens.. 1988;6:805-813. [Medline] [Order article via Infotrieve]
44.
Huang BS, Leenen FHH. Brain ‘ouabain’ and
desensitization of arterial baroreflex by high sodium in
Dahl salt-sensitive rats. Hypertension.. 1995;25:372-376.
45.
Huang BS, Leenen FHH. Brain ‘ouabain,’ sodium,
and arterial baroreflex in spontaneously hypertensive
rats. Hypertension.. 1995;25:814-817.
46. Balzan S, Montali U, Biver P, Ghione S. Digoxin-binding antibodies reverse the effect of endogenous digitalis-like compounds on Na,K-ATPase in erythrocytes. J Hypertens. 1991;9(suppl 6):S304-S305.
This article has been cited by other articles:
 |
|
 |
|
  X. Hu, S. P. Yu, J. L. Fraser, Z. Lu, M. E. Ogle, J.-A. Wang, and L. Wei Transplantation of hypoxia-preconditioned mesenchymal stem cells improves infarcted heart function via enhanced survival of implanted cells and angiogenesis. J. Thorac. Cardiovasc. Surg., April 1, 2008; 135(4): 799 - 808. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Hu, J. Wang, J. Chen, R. Luo, A. He, X. Xie, and J. Li Optimal temporal delivery of bone marrow mesenchymal stem cells in rats with myocardial infarction Eur. J. Cardiothorac. Surg., March 1, 2007; 31(3): 438 - 443. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. A. Dean, J. Tan, R. White, E. R. O'Brien, and F. H. H. Leenen Regulation of components of the brain and cardiac renin-angiotensin systems by 17beta-estradiol after myocardial infarction in female rats Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2006; 291(1): R155 - R162. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. V. Pitzalis, J. M. Hamlyn, E. Messaggio, M. Iacoviello, C. Forleo, R. Romito, E. de Tommasi, P. Rizzon, G. Bianchi, and P. Manunta Independent and incremental prognostic value of endogenous ouabain in idiopathic dilated cardiomyopathy Eur J Heart Fail, March 1, 2006; 8(2): 179 - 186. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Zheng, Y.-F. Li, K. G. Cornish, I. H. Zucker, and K. P. Patel Exercise training improves endogenous nitric oxide mechanisms within the paraventricular nucleus in rats with heart failure Am J Physiol Heart Circ Physiol, May 1, 2005; 288(5): H2332 - H2341. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. S. Huang and F. H. H. Leenen Blockade of brain mineralocorticoid receptors or Na+ channels prevents sympathetic hyperactivity and improves cardiac function in rats post-MI Am J Physiol Heart Circ Physiol, May 1, 2005; 288(5): H2491 - H2497. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Lal, J. P. Veinot, and F. H.H. Leenen Critical role of CNS effects of aldosterone in cardiac remodeling post-myocardial infarction in rats Cardiovasc Res, December 1, 2004; 64(3): 437 - 447. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. S. Huang, B. N. Van Vliet, and F. H. H. Leenen Increases in CSF [Na+] precede the increases in blood pressure in Dahl S rats and SHR on a high-salt diet Am J Physiol Heart Circ Physiol, September 1, 2004; 287(3): H1160 - H1166. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Tan, H. Wang, and F. H. H. Leenen Increases in brain and cardiac AT1 receptor and ACE densities after myocardial infarct in rats Am J Physiol Heart Circ Physiol, May 1, 2004; 286(5): H1665 - H1671. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Wang, B. S. Huang, D. Ganten, and F. H.H. Leenen Prevention of Sympathetic and Cardiac Dysfunction After Myocardial Infarction in Transgenic Rats Deficient in Brain Angiotensinogen Circ. Res., April 2, 2004; 94(6): 843 - 849. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. A. Jortani, S. D. Prabhu, and R. Valdes Jr Strategies for Developing Biomarkers of Heart Failure Clin. Chem., February 1, 2004; 50(2): 265 - 278. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Wang, B. S. Huang, and F. H. H. Leenen Brain sodium channels and ouabainlike compounds mediate central aldosterone-induced hypertension Am J Physiol Heart Circ Physiol, December 1, 2003; 285(6): H2516 - H2523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. B. Felder, J. Francis, Z.-H. Zhang, S.-G. Wei, R. M. Weiss, and A. K. Johnson Heart failure and the brain: new perspectives Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2003; 284(2): R259 - R276. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-Y. Min, Y. Yang, K. L. Converso, L. Liu, Q. Huang, J. P. Morgan, and Y.-F. Xiao Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats J Appl Physiol, January 1, 2002; 92(1): 288 - 296. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Francis, R. M. Weiss, S. G. Wei, A. K. Johnson, and R. B. Felder Progression of heart failure after myocardial infarction in the rat Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2001; 281(5): R1734 - R1745. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Kenney, T. I. Musch, and M. L. Weiss Renal sympathetic nerve regulation to heating is altered in rats with heart failure Am J Physiol Heart Circ Physiol, June 1, 2001; 280(6): H2868 - H2875. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. P. Patel, K. Zhang, and P. K. Carmines Norepinephrine turnover in peripheral tissues of rats with heart failure Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2000; 278(3): R556 - R562. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. H. H. Leenen, B. Yuan, and B. S. Huang Brain "ouabain" and angiotensin II contribute to cardiac dysfunction after myocardial infarction Am J Physiol Heart Circ Physiol, November 1, 1999; 277(5): H1786 - H1792. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. S. Huang, M. Kudlac, R. Kumarathasan, and F. H. H. Leenen Digoxin Prevents Ouabain and High Salt Intake-Induced Hypertension in Rats With Sinoaortic Denervation Hypertension, October 1, 1999; 34(4): 733 - 738. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. S. Huang and F. H. H. Leenen Brain Renin-Angiotensin System and Ouabain-Induced Sympathetic Hyperactivity and Hypertension in Wistar Rats Hypertension, July 1, 1999; 34(1): 107 - 112. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Zhang, B. S. Huang, and F. H. H. Leenen Brain renin-angiotensin system and sympathetic hyperactivity in rats after myocardial infarction Am J Physiol Heart Circ Physiol, May 1, 1999; 276(5): H1608 - H1615. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. H. H. Leenen, V. Skarda, B. Yuan, and R. White Changes in cardiac ANG II postmyocardial infarction in rats: effects of nephrectomy and ACE inhibitors Am J Physiol Heart Circ Physiol, January 1, 1999; 276(1): H317 - H325. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Vahid-Ansari and F. H. H. Leenen Pattern of neuronal activation in rats with CHF after myocardial infarction Am J Physiol Heart Circ Physiol, December 1, 1998; 275(6): H2140 - H2146. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. S. Huang, S. J. Veerasingham, and F. H. H. Leenen Brain "ouabain," ANG II, and sympathoexcitation by chronic central sodium loading in rats Am J Physiol Heart Circ Physiol, April 1, 1998; 274(4): H1269 - H1276. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. S. Huang, B. Yuan, and F. H. H. Leenen Blockade of Brain `Ouabain' Prevents the Impairment of Baroreflexes in Rats After Myocardial Infarction Circulation, September 2, 1997; 96(5): 1654 - 1659. [Abstract] [Full Text]
|
|
|
|
|
|
B. S. Huang, J. M. Sancho, R. Garcia-Robles, and F. H. H. Leenen Sympathoexcitatory Effect of Hypothalamic/ Hypophysary Inhibitory Factor in Rats Hypertension, June 1, 1997; 29(6): 1291 - 1295. [Abstract] [Full Text]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||