A Regional Difference in Endothelium-Dependent Relaxation Responses to Acetylcholine in the Canine Venous System

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Abstract
Endothelium-dependent relaxations of canine veins isolated from 15 different sites were examined. Acetylcholine (ACh, 10-10-10-6 M) caused marked endothelium-dependent relaxations in the external jugular vein, superior vena cava, brachiocephalic vein, segment A (supradiaphragmatic portion) and D (infrarenal portion) of the inferior vena cava. However, only contractile responses were induced by ACh in the portal, mesenteric veins and the segment C of the inferior vena cava (between liver and renal veins) with or without endothelium. The other 7 veins showed only/small endothelium-dependent relaxations (10-20%). These results indicated that the endothelium-dependent responses of canine veins to ACh are regionally different.