Angiotensin II and phorbol ester enhance isoproterenol- and vasoactive intestinal peptide (VIP)-induced cyclic AMP accumulation in vascular smooth muscle cells.

The importance of Ca2+ and cAMP in the regulation of cellular functions has been well demonstrated. We studied the effect of angiotensin II (AII), a potent Ca2+-mobilizing hormone, on cAMP accumulation induced by isoproterenol (ISO) and vasoactive intestinal peptide (VIP) in cultured vascular smooth muscle cells (VSMC). Although the addition of AII alone caused little increase of cAMP, it enhanced ISO- and VIP-induced cAMP accumulations in a dose-dependent manner. This enhancement was mimicked by tumor-promoting phorbol ester but not by Ca2+ ionophore. This observation suggested that AII enhanced agonist-induced cAMP accumulation through the activation of protein kinase C in VSMC.