Published online before print June 5, 2003, doi: 10.1161/01.RES.0000080318.81205.FD
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Submitted on October 9, 2002
Revised on May 23, 2003
Accepted on May 23, 2003
Homocellular Conduction Along Endothelium and Smooth Muscle of Arterioles in Hamster Cheek Pouch. Unmasking an NO Wave
Stéphane Budel ;
From the John B. Pierce Laboratory and Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Conn.
* To whom correspondence should be addressed. E-mail: sssegal{at}jbpierce.org.
We investigated roles for homocellular (endothelium or smooth muscle) and heterocellular (myoendothelial) conduction pathways along hamster cheek pouch arterioles in vivo (n=64; diameter, 33±1 µm). Endothelium-dependent and -independent vasoactive agents were delivered from micropipettes (0.5 or 1 second pulse) onto an arteriole while observing diameter changes at defined distances along the vessel. Acetylcholine (ACh) produced maximal diameter (63±1 µm) locally and vasodilation conducted rapidly (
10 µm response at 2 mm, <1 second). Responses to bradykinin (BK) were similar, whereas sodium nitroprusside produced maximal dilation locally without conduction. KCl evoked biphasic conduction of vasoconstriction and vasodilation, whereas phenylephrine (PE) produced conducted vasoconstriction. Disrupting the integrity of endothelium as a conduction pathway using focal light-dye treatment (LDT) abolished conducted vasodilation to BK and to KCl but not to ACh. Disruption of smooth muscle integrity with LDT abolished conducted vasoconstriction with no effect on conducted vasodilation. After LDT of respective cell layers at sites 1 mm apart, vasodilation to ACh conducted past disrupted smooth muscle or disrupted endothelium, but not beyond both sites in series. The loss of conduction after selective LDT indicates a lack of effective myoendothelial coupling along the arteriolar wall. During NO synthase inhibition (L-NA, 100 µmol/L), conducted vasodilation was abolished to BK and to KCl yet remained intact to ACh. However, after LDT of smooth muscle, L-NA inhibited conduction to ACh by 60%. Thus, conduction of vasodilation entails a wave of NO release along arteriolar endothelium that is masked when smooth muscle provides a parallel conduction pathway.
Key words: microcirculation • conduction • endothelium • smooth muscle • nitric oxide
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