2008 Volume 108 Issue 1 Pages 95-103
Vascular endothelium regulates vascular tone by releasing endothelium-derived vasoactive substances. We performed this study to characterize the inhibitory effect of the endothelium on vasoconstrictor stimuli in rat mesenteric vascular beds. Changes in perfusion pressure induced by continuous perfusion of Krebs solution containing methoxamine (α1-adrenoceptor agonist) or high KCl were measured over 180 min. In preparations with intact endothelium, methoxamine-induced vasoconstriction was time-dependently decreased to cause 60% – 80% reduction of the initial vasoconstriction level, while no reduction was observed in high-KCl–induced vasoconstriction. Endothelium removal significantly blunted the time-dependent reduction of methoxamine-induced vasoconstriction without affecting high-KCl–induced vasoconstriction. Neither a nitric oxide synthase inhibitor (