Angiotensin II attenuates vascular contractility in the rabbit mesenteric artery

We observed the effects of angiotensin II (AII) on the contractile response 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 increasing 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 response of the contraction. The change in [Ca2+]i induced by high K+ solution, however, was not significantly different with and without treatment with AII. Pretreatment of the tissue with actinomycin D abolished the 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 Ca(2+)-sensitivity of the contractile machinery.