ANGIOTENSIN-II ATTENUATES VASCULAR CONTRACTILITY IN THE RABBIT MESENTERIC-ARTERY

We observed the effects of angiotensin II (AII) on the contractile res ponse and the Ca2+ transient induced by high K+ solution in the rabbit mesenteric artery. In the control condition, the repeated application of high K+ solution with 90 min interval induced a gradually increasi ng contraction, which was accompanied with a significant elevation of the intracellular calcium concentration ([Ca2+](i)). Treatment of the tissue with AII for one to two hours abolished the incremental respons e of the contraction. The change in [Ca2+](i) induced by high K+ solut ion, however, was not significantly different with and without treatme nt with AII. Pretreatment of the tissue with actinomycin D abolished t he inhibitory action of AII on the incremental contraction, indicating the involvement of a transcriptional process. These results indicate that AII impairs vascular contractility through the modulation of Ca2-sensitivity of the contractile machinery. (C) 1996 Academic Press, In c.