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Arteriolar Occlusion Causes Independent Cellular Responses in Endothelium and Smooth Muscle
Author(s) -
CHEN YIFAN,
RIVERS RICHARD J.
Publication year - 2002
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.1038/sj.mn.7800158
Subject(s) - occlusion , chemistry , vasoconstriction , endothelium , anatomy , vasodilation , vascular smooth muscle , arteriole , medicine , smooth muscle , microcirculation
Objectives : To test the hypothesis that arteriolar occlusion causes different cellular changes in endothelial and smooth muscle cells. Methods : Cheek pouch arterioles (resting diameter 41 ± 2 µm) of anesthetized hamsters were occluded briefly (<60 seconds) either upstream or downstream from an observation site. Changes in membrane potential and intracellular calcium concentration ([Ca 2+ ] i ) of the endothelial or smooth muscle cells were determined by using fluorescence microscopy (ratiometric analysis). Results : The pressure in the occluded segment decreased by 17.4 ± 2.6 cm H 2 O during upstream occlusion and increased by 16.8 ± 6 cm H 2 O during downstream occlusion ( n = 5). Upstream occlusion caused vasoconstriction of the occluded segment by 2.4 ± 0.4 µm, whereas downstream occlusion produced brief vasodilatation by 1.1 ± 0.2 µm. The endothelial cells hyperpolarized during upstream or downstream occlusion (ratio change: 2.26 ± 0.24% and 2.39 ± 0.42%, respectively; p < 0.01, n = 5). There were no changes in endothelial [Ca 2+ ] i . The smooth muscle cells depolarized (ratio change: −2.08 ± 0.14%, n = 5) with an increase in [Ca 2+ ] i (ratio change: 2.92 ± 0.16%, n = 6) during downstream occlusion. However, there was no detectable change in membrane potential or [Ca 2+ ] i of smooth muscle cells during upstream occlusion. All the changes rapidly recovered when occlusion was released. Responses of an in‐situ isolated segment on a side branch revealed conducted dilatory signals caused by the occlusions. Conclusions : Our results show that the endothelial and smooth muscle cells respond independently to arteriolar occlusion. The endothelial and smooth muscle cells do not effectively communicate in [Ca 2+ ] i or membrane potential during acute arteriolar occlusion. Hyperpolarizing signals in endothelium cause conducted dilation.