Potentiating Effects of Angiotensin II on Norepinephrine-Induced Vasoconstriction in Isolated and Perfused Dog Mesenteric Arteries

Abstract

Effects of angiotensin II on norepinephrine and KCl-induced vasoconstrictions were investigated in isolated canine mesenteric arteries which were perfused with Krebs' solution at 37°C. Angiotensin I I at 0.03-0.3 μg showed tachyphylaxis in the injection intervals used (10, 20 or 30 min intervals). After treatment with angiotensin II (0.18-1.8 μg), norepinephrine and KCl-induced constrictions were consistently potentiated. Imipramine which blocked tyramineinduced action did not significantly influence norepinephrine-induced constriction. Pretreatments with both angiotensin II and indomethacin enhanced norepinephrine-induced constriction much greater than that with angiotensin II alone. It is suggested that angiotensin II may modify intracellular Ca movements and prostaglandin production induced by norepinephrine.