EFFECTS OF PROTEIN-KINASE-C ACTIVATION ON NOREPINEPHRINE-INDUCED PHOSPHATIDYLINOSITIDE HYDROLYSIS IN INTACT RAT AORTA

The purpose of this study was to investigate the role of protein kinase C in the regulation of alpha1-adrenoceptor-mediated phosphatidylinositide hydrolysis in intact vascular smooth muscle. Phorbol myristate acetate (0.1 and 1 muM) and staurosporine inhibited and potentiated, respectively, norepinephrine-induced inositol phosphate formation in intact rat aorta. In contrast, 30 muM prostaglandin F2alpha, which activated protein kinase C to a similar magnitude as 1 muM phorbol myristate acetate, was without effect on norepinephrine-induced inositol phosphate formation. These results suggest that protein kinase C activated in response to physiologic agonists, but not in response to phorbol esters, may be compartmentalized within the smooth muscle cell.