Articles

Comparison of Aorta and Pulmonary Artery

I. Early Cholesterol Accumulation and Relative Susceptibility to Atheromatous Lesions

Dawn C. Schwenke
https://doi.org/10.1161/01.RES.81.3.338
Circulation Research. 1997;81:338-345
Originally published September 19, 1997

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Abstract

Abstract In rabbits, the pulmonary artery and the aorta are susceptible to atherosclerosis. However, susceptibility of the pulmonary artery, compared with the aortic arch, to atherosclerosis and the relationship between the accumulation of cholesterol during the early stages of atherogenesis and the development of atheromatous lesions for these arterial regions remain to be clarified. Cholesterol concentrations for the pulmonary artery and aorta were measured in normal rabbits and in rabbits fed a 0.5% cholesterol diet for 8, 12, and 16 days and 17 weeks. In normal rabbits, the rank order of arterial cholesterol concentrations was pulmonary artery>aortic arch>descending thoracic aorta, with concentrations of total and nonesterified cholesterol 17% and 25% (both P<.05) greater, respectively, for the pulmonary artery than for the descending thoracic aorta. Rank order remained the same during 16 days of cholesterol feeding, but differences between arterial regions were exaggerated. After rabbits were fed cholesterol for 16 days, total and esterified cholesterol concentrations were 57% and 920% (both P<.01) greater, respectively, for the pulmonary artery than for the descending thoracic aorta, with much smaller differences between the aortic regions. In contrast, after rabbits were fed cholesterol for 17 weeks, concentrations of total, esterified, and nonesterified cholesterol were similar for the pulmonary artery and aortic arch, but these forms of cholesterol were increased 100%, 130%, and 53% (all P<.03), respectively, for the aortic arch compared with the descending thoracic aorta. Cholesterol concentrations for the pulmonary artery were positively associated with those for the aortic regions during the first 16 days of cholesterol feeding, but for rabbits fed cholesterol for 17 weeks the associations were either negative or absent. These results indicate that relative rates of cholesterol accumulation in the pulmonary artery and aorta differ at different stages of atherogenesis and suggest that the balance between processes that deliver cholesterol to, and remove cholesterol from, the artery may change in different ways in these arterial regions during atherogenesis.

Rabbits with dietary-induced1 2 3 4 5 6 7 8 9 and spontaneous hypercholesterolemia10 11 12 develop atherosclerotic lesions in the pulmonary artery. If hemodynamics play a role in atherosclerosis, as data suggest,13 14 15 16 the much lower blood pressure in the pulmonary artery than in the aorta17 would suggest that the pulmonary artery would be less susceptible to atherosclerosis than the aorta. However, the pulmonary artery and aortic arch (the part of the aorta with similar proximity to the heart as the pulmonary artery) also differ in structure, thickness, and cellularity17 18 ; it is not clear how this combination of factors would influence atherosclerosis. Some studies in rabbits fed cholesterol reported that pulmonary artery atherosclerosis was less extensive than aortic atherosclerosis,3 5 8 19 whereas another study suggested that pulmonary atherosclerosis was at least as extensive as aortic atherosclerosis.6 Although susceptibility to atherosclerosis within the aorta decreases with increasing distance from the heart,6 11 12 20 21 22 23 only two studies involving relatively few rabbits1 6 compared atherosclerosis in the pulmonary artery with that in the aortic arch. These studies suggest that pulmonary atherosclerosis was at least as severe as that in the aortic arch.1 6

We reported that focal atherosclerosis-susceptible areas within the aorta accumulate cholesterol more rapidly during short intervals of cholesterol feeding than do the surrounding atherosclerosis-resistant aortic regions.24 However, there are little if any quantitative data in the literature concerning the early stages of atherosclerosis in the pulmonary artery compared with the aorta and for the entire descending thoracic and arch regions of the thoracic aorta. In addition, a study that considered different intervals of dietary treatment reported inconsistent results for differences between atherosclerosis in the pulmonary artery and the aorta as a whole.4 Thus, atherogenesis in the pulmonary artery and different aortic regions remains to be clarified.

One aim of the present study was to characterize cholesterol accumulation in the aortic arch and pulmonary artery of normal rabbits and in rabbits after short intervals of cholesterol feeding. The descending thoracic aorta was also studied as a reference aortic region that is less susceptible to atherosclerosis than is the aortic arch.6 11 12 20 21 22 23 The second aim of the present study was to assess the relative susceptibility of the aortic arch and pulmonary artery to atherosclerosis. Finally, we sought to determine whether arterial cholesterol accumulation after short intervals of cholesterol feeding would accurately predict relative susceptibility to atherosclerosis for the pulmonary artery, aortic arch, and descending thoracic aorta.

Materials and Methods

Rabbits

These studies used sexually mature young female New Zealand White rabbits. Short-term arterial cholesterol accumulation was studied in 43 rabbits (33 rabbits from Franklin’s Rabbitry and Supply, Wake Forest, NC, and 10 rabbits from Robinson Services, Inc, Winston-Salem, NC). The source of rabbits did not influence arterial cholesterol. Development of atheromatous lesions was studied in 8 rabbits from Robinson Services, Inc. After acclimation to the animal facilities24 and before entering the studies, rabbits weighed ≈2.5 kg. Rabbits weighed 2.60±0.04 kg (mean±SEM, n=42) at the end of the study of short-term cholesterol accumulation and 3.28±0.07 kg (n=8) at the end of the study of atheromatous lesion formation. Rabbits were studied while they consumed either cholesterol-free rabbit chow (Prolab) or the same diet supplemented with cholesterol and 2.5% corn oil. The cholesterol concentration in the diet was 0.5%, except as noted in Table 1⇓. All rabbits were fed 100 g of their respective diets each day. Blood samples (1 mL) were collected24 after an overnight fast while the rabbits were consuming cholesterol-free rabbit chow. Additional samples were collected every 4 days for rabbits fed cholesterol for ≤16 days and every 2 weeks for rabbits fed cholesterol for 17 weeks. All blood samples were collected into 0.01 vol of 0.4 mol/L EDTA.

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Table 1.

Lipids and Lipoproteins

Plasma and Lipoprotein Cholesterol Concentrations

Blood samples were collected after an overnight fast from all rabbits just before they were euthanized to measure plasma and lipoprotein (only for rabbits fed cholesterol for 17 weeks) cholesterol concentrations. Lipoproteins (VLDL+IDL, LDL, and HDL) were isolated by differential centrifugation25 as d<1.020, 1.020<d<1.060, and d>1.060 g/mL plasma fractions, respectively. Plasma and lipoprotein cholesterol concentrations were measured by an enzymatic method.26

Arterial Sampling

Most rabbits were euthanized by an overdose of pentobarbital sodium (100 mg/kg body wt). A few were exsanguinated after they were deeply anesthetized with ketamine hydrochloride and xylazine (60 and 6 mg/kg body wt, respectively). Similar numbers of untreated rabbits and those fed cholesterol for 8, 12, and 16 days were studied at a given time. The rabbits fed cholesterol for 17 weeks were studied in a separate experiment.

The aorta and pulmonary artery trunk were removed with the heart. These arteries were separated from the heart.27 Thoracic and abdominal regions of the aorta were separated.24 After adventitial tissue was removed, the thoracic aorta and pulmonary artery were opened longitudinally and pinned flat.28 29 30 These arterial samples were photographed both before and after separating the aortic arch from the descending thoracic aorta.24 Arterial samples were kept at 4°C whenever possible and were weighed and frozen at −20°C until analysis. Surface areas of arterial samples from rabbits fed cholesterol for 17 weeks were measured.28 29 30 The thickness of atheromatous arteries was calculated by dividing fresh weights of arterial samples by the product of the corresponding arterial surface areas and arterial density. The density of fresh artery was estimated from the density of fixed rabbit artery31 and data for dehydration of rabbit thoracic aorta upon fixation.30

Arterial Cholesterol Concentrations

Lipids were extracted from arterial samples with 2:1 (vol/vol) chloroform/methanol.24 32 For the study of short-term arterial cholesterol accumulation, esterified and nonesterified cholesterol in solvent extracts were separated by thin-layer chromatography.24 Total cholesterol (all samples) and nonesterified cholesterol (most samples) were determined as described previously.24 33 34 For the study of arterial cholesterol accumulation in rabbits fed cholesterol for 17 weeks, both total and nonesterified cholesterol concentrations were measured in solvent extracts by enzymatic methods using cholesterol esterase and cholesterol oxidase and using only cholesterol oxidase, respectively.35 Esterified cholesterol concentrations in arterial samples were determined as the difference between the measured total and nonesterified cholesterol concentrations. Each cholesterol assay included a solvent extract of a control sample (level 2, Solomon Park). For the study of short-term cholesterol accumulation, mean intraassay and interassay coefficients of variation for this control sample were 3.6% and 8.3%, respectively. For total and nonesterified cholesterol measured in arteries of rabbits fed cholesterol for 17 weeks, intraassay coefficients of variation were 2.7% and 1.8%, respectively; interassay coefficients of variation were 1.2% and 1.2%, respectively.

Cholesterol Exposure Index

The arterial exposure to elevated plasma cholesterol (cholesterol exposure index) was calculated by determining the area under the curve of the increment in plasma cholesterol concentration above the normal value versus time of cholesterol feeding as described previously.24

Statistical Methods

The three arterial regions were compared by ANOVA with a multiple-measures design.36 When necessary to stabilize variances among arterial regions, data were transformed to logarithms before ANOVA. When the ANOVA was significant, pairwise comparisons were performed among the three arterial regions.37 Pairwise comparisons of arterial regions after different intervals of cholesterol feeding were performed by ANOVA with multiple measures for arterial regions and by grouping data according to the duration of cholesterol feeding.36 Probability values were adjusted using the Bonferroni criteria to account for multiple comparisons.38 Other comparisons were performed by the method of Scheffé.37 Regression analysis was used to investigate the relationship between arterial cholesterol concentrations and both duration of cholesterol feeding and cholesterol exposure index.24 37 Correlations between cholesterol concentrations in different arterial regions were also determined.37 A value of P<.05 was considered significant.

Results

Cholesterol Concentrations for Arterial Regions of Normal Rabbits

For normal rabbits, the rank order for total and nonesterified cholesterol was pulmonary artery>aortic arch>descending thoracic aorta (Table 2⇓). Most of the differences among arterial regions were due to higher values for the pulmonary artery.

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Table 2.

Arterial Cholesterol During the First 16 Days of Cholesterol Feeding

Changes in Arterial Cholesterol Concentrations During the First 16 Days of Cholesterol Feeding

Total cholesterol concentrations increased for the pulmonary artery and aortic arch. Esterified cholesterol concentrations increased only for the pulmonary artery; nonesterified cholesterol concentrations increased for all arterial regions (Table 2⇑). Throughout the 16-day period of cholesterol feeding, the rank order for total and nonesterified cholesterol remained pulmonary artery>aortic arch>descending thoracic aorta, but differences among arterial regions were exaggerated. For the entire 16 days of cholesterol feeding considered as a whole, concentrations of total, esterified, and nonesterified cholesterol were consistently higher for the pulmonary artery compared with the aortic regions. Interestingly, the percentage of cholesterol esterified was consistently higher for the pulmonary artery compared with the aortic regions.

Morphological Features of Atheromatous Aorta and Pulmonary Artery

For rabbits fed cholesterol for 17 weeks, the rank order for atherosclerotic lesion areas and arterial thickness was aortic arch>pulmonary artery>descending thoracic aorta (Table 3⇓). Atherosclerotic lesion areas differed among regions, but no pairwise comparisons were significant. In contrast, all pairwise comparisons were significant for arterial thickness.

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Table 3.

Atheromatous Arteries After 17 Weeks of Cholesterol Feeding

Cholesterol in Atheromatous Aorta and Pulmonary Artery

Whether expressed per unit weight or per unit surface area, the rank order for total and nonesterified cholesterol was aortic arch>pulmonary artery≥descending thoracic aorta (Table 3⇑). The rank order for esterified cholesterol differed on a weight basis (pulmonary artery>aortic arch) and on a surface-area basis (aortic arch>pulmonary artery). The rank order for percentage of cholesterol esterified was pulmonary artery>aortic arch>descending thoracic aorta. The only significant differences between pulmonary artery and aortic arch were for nonesterified cholesterol per unit surface area and percentage of cholesterol esterified. In contrast, all differences between aortic arch and descending thoracic aorta were significant.

Relationship Between Arterial Cholesterol and Cholesterol Exposure Index

For normal rabbits and those fed cholesterol for up to 16 days combined, arterial total cholesterol concentrations were positively associated with the cholesterol exposure index for the pulmonary artery and aortic arch (Fig 1⇓, left side, top and middle panels). Surprisingly, for rabbits fed cholesterol for 17 weeks, arterial total cholesterol concentrations were not associated with the cholesterol exposure index for any arterial region (Fig 1⇓, right side).

Figure 1.
Figure 1.

Relationship between cholesterol exposure index and arterial cholesterol concentration for pulmonary artery (top), aortic arch (middle), and descending thoracic aorta (bottom). Left, Data for rabbits fed cholesterol for 0 to 16 days. ♦ indicates rabbits never fed cholesterol (n=12); •, rabbits fed cholesterol for 8 days (n=11); ▴, rabbits fed cholesterol for 12 days (n=9); and ▪, rabbits fed cholesterol for 16 days (n=11). Right, Rabbits fed cholesterol for 17 weeks (n=8). Regression lines were determined from all the data shown. When the apparent outlier in the top left panel was excluded, the r value was reduced to .42, and the P value was .007. The slope of the regression line was also reduced but was still 68% greater than that for the aortic arch of the same rabbits.

For rabbits fed cholesterol up to 16 days, arterial esterified cholesterol concentrations were also related to the cholesterol exposure index for the pulmonary artery, with a trend for the aortic arch (data not shown). In comparison, for rabbits fed cholesterol for 17 weeks, neither arterial esterified nor nonesterified cholesterol was related to the cholesterol exposure index for any arterial region (data not shown).

Relationship Between the Pulmonary Artery and the Two Aortic Regions for Cholesterol Accumulation in Rabbits Fed Cholesterol for up to 16 Days

There was a positive association between the pulmonary artery and aortic arch for accumulation of total, esterified, and nonesterified cholesterol (Fig 2⇓, left side). Similar associations were found between the pulmonary artery and descending thoracic aorta for accumulation of total and nonesterified cholesterol (Fig 2⇓, right side).

Figure 2.
Figure 2.

Relationship between cholesterol concentrations of pulmonary artery and those of the aortic regions for normal rabbits and for rabbits fed cholesterol for up to 16 days (total cholesterol [top], esterified cholesterol [middle], and nonesterified cholesterol [bottom]). Left, Relationship between cholesterol concentrations for pulmonary artery and aortic arch. Right, Relationship between cholesterol concentrations for pulmonary artery and descending thoracic aorta. ♦ indicates rabbits never fed cholesterol (n=12 [total cholesterol] and n=11 [esterified and nonesterified cholesterol]; •, rabbits fed cholesterol for 8 days (n=11 [total cholesterol] and n=10 [esterified cholesterol and nonesterified cholesterol]); ▴, rabbits fed cholesterol for 12 days (n=9 [total, esterified, and nonesterified cholesterol]); and ▪, rabbits fed cholesterol for 16 days (n=11 [total cholesterol] and n=9 [esterified and nonesterified cholesterol]). Regression lines shown were determined from all the data shown. When the apparent outliers for total and nonesterified cholesterol were excluded, r values for regression were increased to .74 and .83 for total cholesterol for aortic arch and descending thoracic aorta, respectively, and increased to .70 and .80 for nonesterified cholesterol for aortic arch and descending thoracic aorta, respectively (all P<.0001).

Relationship Between Pulmonary Artery and the Aortic Regions for Cholesterol Accumulation and Atheromatous Lesions in Rabbits Fed Cholesterol for 17 Weeks

There was an inverse relationship between pulmonary artery and aortic arch for accumulation of both total and esterified cholesterol (Fig 3⇓, left side). Nonsignificant trends in the same direction were observed between the pulmonary artery and aortic arch for nonesterified cholesterol and for associations between the pulmonary artery and descending thoracic aorta for accumulation of all forms of cholesterol (Fig 3⇓, right side). Surface areas of atheromatous lesions in the pulmonary artery were not related to surface areas of atheromatous lesions in either the aortic arch (Fig 3⇓, bottom left) or descending thoracic aorta (Fig 3⇓, bottom right).

Figure 3.
Figure 3.

Relationship between atheromatous lesions of pulmonary artery and those of aorta for rabbits fed cholesterol for 17 weeks (n=8) (top to bottom, total cholesterol, esterified cholesterol, nonesterified cholesterol, and percent surface area covered by atheromatous lesions). Left, Relationship between atheromatous lesions of pulmonary artery and aortic arch. Right, Relationship between atheromatous lesions of pulmonary artery and descending thoracic aorta.

Relationship Between Aortic Arch and Descending Thoracic Aorta for Cholesterol Accumulation and Atheromatous Lesions

For normal rabbits and those fed cholesterol for up to 16 days combined, there was a strong positive association between the aortic arch and descending thoracic aorta for accumulation of both total and nonesterified cholesterol (Fig 4⇓, left side). Similar relationships were present for these forms of cholesterol for rabbits fed cholesterol for 17 weeks (Fig 4⇓, right side). At this time, there were also strong positive associations between the aortic arch and descending thoracic aorta for esterified cholesterol and for areas of atheromatous lesions (Fig 4⇓, bottom right). Interestingly, associations between the aortic arch and descending thoracic aorta for all forms of cholesterol for rabbits fed cholesterol for 17 weeks were consistently at least as strong as the corresponding associations for rabbits fed cholesterol for up to 16 days.

Figure 4.
Figure 4.

Relationship between cholesterol accumulation and atheromatous lesions in aortic arch and in descending thoracic aorta (top to bottom, total cholesterol, esterified cholesterol, nonesterified cholesterol, and surface area of atheromatous lesions). Left, Data for rabbits fed cholesterol for 0 to 16 days. ♦ indicates rabbits never fed cholesterol (n=12); •, rabbits fed cholesterol for 8 days (n=11); ▴, rabbits fed cholesterol for 12 days (n=9); and ▪, rabbits fed cholesterol for 16 days (n=11). Right, Rabbits fed cholesterol for 17 weeks (n=8).

Discussion

In the present study, we sought to characterize cholesterol accumulation during early cholesterol feeding and relative susceptibility to atherosclerosis for the pulmonary artery, aortic arch, and descending thoracic aorta. We also investigated whether relative susceptibility of these regions to atherosclerosis was related to the time dependence of cholesterol accumulation during short intervals of cholesterol feeding. In the present study, we report that atheromatous lesion development in rabbits fed cholesterol for 17 weeks was similar for the aortic arch and pulmonary artery, with more extensive atherosclerosis in the aortic arch than in the descending thoracic aorta. These data are consistent with the more rapid cholesterol accumulation in the pulmonary artery and aortic arch than in the descending thoracic aorta during the first 16 days of cholesterol feeding. However, total, esterified, and nonesterified cholesterol concentrations were consistently higher for the pulmonary artery than for the aortic arch during the first 16 days of cholesterol feeding, in contrast to atheromatous lesion development after 17 weeks of cholesterol feeding.

Atherosclerosis in Pulmonary Artery and Aortic Arch

Data for susceptibility of the pulmonary artery and aortic arch to atherosclerosis are inconsistent. Some studies3 4 8 19 found the atherosclerotic lesion area to be reduced in the pulmonary artery compared with the entire aorta. Because the atherosclerotic lesion area for the entire aorta is only 1/4 to 1/2 of that for the aortic arch,6 11 12 22 23 one could infer that those studies found reduced atherosclerosis in the pulmonary artery compared with the aortic arch. In contrast, other studies that directly compared atherosclerosis in the pulmonary artery and aortic arch found the atherosclerotic lesion area6 and arterial cholesterol concentrations1 to be at least as great for the pulmonary artery as for the aortic arch and greater than for the descending thoracic aorta. Our data agree with the direct comparisons of atherosclerosis in the pulmonary artery and aortic arch.

Arterial Esterified Cholesterol

An earlier study in rabbits reported a higher percentage of cholesterol to be esterified in the pulmonary artery compared with the aortic arch.1 Our data for 12 days, 16 days, and 17 weeks of cholesterol feeding are consistent with that report. Most esterified cholesterol in atherosclerotic lesions is in foam cells, many of which are derived from macrophages.39 40 41 In contrast, nonesterified cholesterol accumulating after cholesterol feeding is first found in extracellular vesicles42 43 44 ; later it appears as cholesterol clefts.45 46 It is possible that macrophage recruitment into the pulmonary artery is more efficient than recruitment into the aortic arch early in cholesterol feeding and that increased macrophage density persists in the pulmonary artery during atherogenesis. The higher percentage of esterified cholesterol in the pulmonary artery compared with the aortic arch might suggest that either acylcholesterol:acyltransferase activity was increased or lysosomal cholesterol hydrolysis was reduced in the pulmonary artery. Such an imbalance could reduce the pool of nonesterified cholesterol available for efflux.

Association of Arterial Cholesterol Accumulation With Plasma Cholesterol

Cholesterol accumulation in the aortas of rabbits fed cholesterol for several months47 48 49 and that in atherosclerosis-susceptible aortic sites in rabbits fed cholesterol for up to 16 days24 is positively associated with the cholesterol exposure index. Our data for aortic arch and pulmonary artery for rabbits fed cholesterol for up to 16 days are consistent with the earlier work. Surprisingly, arterial cholesterol accumulation in rabbits fed cholesterol for 17 weeks was not related to the cholesterol exposure index. It is possible that development of fibrous caps over atheromatous lesions50 limited the delivery of cholesterol to arterial cells by reducing arterial LDL degradation,51 thus uncoupling the relationship between hypercholesterolemia and atherosclerotic lesion development.

Model for Atherogenesis in Pulmonary Artery and Aorta

Our data and that of others4 5 are consistent with the hypothesis that atherogenesis proceeds at different rates in the pulmonary artery and aortic arch at different stages of atherogenesis: initially, the rate of cholesterol accumulation in the pulmonary artery exceeds that in the aortic arch, but at some later stage of atherogenesis, this rate slows and becomes lower than that for the aortic arch. In comparison, this and other studies1 6 11 12 20 21 22 23 show that atherogenesis in the aortic arch and descending thoracic aorta of rabbits occurs in parallel but at an increased rate in the aortic arch compared with the descending thoracic aorta.

The high correlation between data for pulmonary artery and aortic arch for cholesterol accumulation during the first 16 days of cholesterol feeding but the lack of such a correlation after 17 weeks of cholesterol feeding might suggest the following: mechanism(s) contributing to atherogenesis in the pulmonary artery and aorta early after the onset of cholesterol feeding are similar, but at later stages, the mechanism(s) contributing to atherogenesis in these regions differ. A companion study27 shows that the delivery of cholesterol to cells of the pulmonary artery and aortic arch via the degradation of LDL was similar in normal rabbits. There were subtle changes in the interaction of LDL with these arterial regions in rabbits fed cholesterol for ≈8 days, which, if exaggerated after longer periods of cholesterol feeding, could contribute to the reduced rate of cholesterol accumulation in the pulmonary artery compared with the aortic arch at later stages of atherogenesis.27 Alternatively or additionally, it is possible that cholesterol efflux from the pulmonary artery becomes more efficient than that from the aortic arch at later stages of atherogenesis. Such changes in the mechanism(s) contributing to atherogenesis in pulmonary artery and aortic arch could provide an explanation for the apparent change in rate of progression of atherosclerosis in these arterial regions.

In summary, we found atheromatous lesion development in rabbits after 17 weeks of cholesterol feeding to be similar for the pulmonary artery and aortic arch and to be increased in the aortic arch compared with the descending thoracic aorta. Results from the first 16 days of cholesterol feeding were in partial agreement with the longer study; more cholesterol accumulated in the pulmonary artery and aortic arch than in the descending thoracic aorta. However, during the first 16 days of cholesterol feeding, cholesterol accumulation in the pulmonary artery exceeded that in the aortic arch. The results of the present study suggest that the relative rates of cholesterol accumulation in the pulmonary artery and the aortic arch differ at different stages of atheromatous lesion development. Such differences may indicate that the balance of processes delivering cholesterol to, and removing cholesterol from, arterial regions shifts in different ways in the pulmonary artery and the aortic regions during the development of atherosclerosis.

Selected Abbreviations and Acronyms

d=density fraction
HDL=high-density lipoprotein
IDL=intermediate-density lipoprotein
LDL=low-density lipoprotein
VLDL=very-low-density lipoprotein

Acknowledgments

This study was supported by National Institutes of Health grant HL-45027. Dr Schwenke is an Established Investigator of the American Heart Association. The author gratefully acknowledges the skillful technical assistance of Christina Tulbert, Elizabeth Ann Jordan, Deanna Warren, and John Mason.

Footnotes

  • Reprint requests to Dawn C. Schwenke, PhD, Department of Pathology, Bowman Gray School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1072.

  • Received February 14, 1997.
  • Accepted June 6, 1997.

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  • Comparison of Aorta and Pulmonary Artery
    Dawn C. Schwenke
    Circulation Research. 1997;81:338-345, originally published September 19, 1997
    https://doi.org/10.1161/01.RES.81.3.338
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