Insulin inhibits vasopressin-elicited contraction of vascular smooth muscle cells

Insulin may play a role in regulation of blood pressure, as indicated by previous observations of insulin-induced reductions in vascular contraction and an association of hypertension with insulin resistance. This study was designed to determine if vascular effects of insulin are mediated, in part, by a direct inhibitory action on the contractility of vascular smooth muscle cells (VSMC). Contractile responses of rat tail arterial VSMC cultured for 4 to 6 days to arginine vasopressin (AVP) were studied using video morphometry. AVP caused dose-dependent contraction of VSMC over the concentration range of 10^-9 M to 10^-5 M (analysis of variance [ANOVA], p < .01). Insulin, by itself, had no effect on VSMC shape; however, insulin, in concentrations ranging from 100 μU/ml to 100 mU/ml, reduced the contractile response to 10^-7M AVP (ANOVA, p < .01). Inhibitory effects of insulin on VSMC contraction were thus obtained at concentrations (e.g., 100 μ U/ml) within the physiologic range of plasma insulin concentrations, suggesting that insulin action on VSMC in vivo may mediate physiologic and pathologic effects of insulin on blood pressure.