Effect of pregnancy on insulin metabolism in spontaneously hypertensive rats

Several lines of evidence suggest that insulin resistance and/or hyperinsulinemia may play an important role in the pathogenesis of hypertension. We studied the effect of pregnancy on insulin metabolism in spontaneously hypertensive rats (SHRs) and in Wistar-Kyoto rats (WKYs) as a control. Pregnancy markedly reduced blood pressure in both strains of rats, but insulin resistance as determined by the hyperinsulinemic glucose clamp (10 mU/kg/min) increased in SHRs and was unchanged in WKYs. The plasma insulin response to an intravenous glucose challenge in SHRs was low and did not change with pregnancy. Therefore, it is suggested that the regulation of blood pressure in these animals is linked to an unknown factor rather than to insulin resistance and hyperinsulinemia. Fetuses from SHRs had a lower body weight and plasma glucose level and higher plasma insulin and pancreatic insulin levels than those from WKYs. Thus, fetal hyperinsulinemia in the SHR may be linked to the development of hypertension in adulthood.