Comparison of the Effects of Angiotensin II and Vasopressin on Cytosolic Free Calcium Concentration, Protein Kinase C Activity, and Prostacyclin Production in Cultured Rat Aortic and Mesenteric Smooth Muscle Cells

Abstract

Differences in responsiveness of various vascular beds to pressor hormones have been reported. In our study, we have examined the effects of angiotensin II (Ang II) and vasopressin (AVP) on cytosolic free Ca2+ concentration ([Ca2+ ]c), protein kinase C (PKC) activity, and prostacyclin (PGI2) production in cultured aortic and mesenteric smooth muscle cells obtained from female Wistar rats. [Ca2+ ]c was determined using the Ca2+ fluorescent probe fura-2. PKC activity was assessed by the measurement of the phosphorylation of histone III-S, in the presence or absence of phospholipids, both in the cytosolic and paniculate fractions. PGI2 production was estimated by a specific radioimmunoassay of its stable metabolite, 6-keto-PGF1α. Our results demonstrate that basal production of PGI2 was higher in mesenteric than in aortic smooth muscle cells. In mesenteric cells, the [Ca2+ ]c, PKC activity, and PGI2 responses to AVP were higher than those induced by Ang II. This situation is the opposite of that observed in aortic smooth muscle cells. These results indicate different sensitivities to AVP and Ang II between vascular smooth muscle cells originating from two types of vessels.