Diabetes-induced changes in the contractility of the aorta and pA2 of nifedipine in the rat

Diabetes-induced changes in the calcium influx and contractile responses of aortic rings to various drugs were investigated in streptozotocin-treated rats. Diabetes is associated with calcium influx into the aortic rings (1.5- and 2.5-fold, respectively, after either KCl or noradrenaline stimulation compared with normal). The maximum KCI-induced contraction of the arorta in diabetic rats was reduced by 38%, but the EC(50) of KCl remained unchanged. The pA(2) of nifedipine for inhibiting the contractile response of aorta to KCl decreased one order of magnitude in the diabetic rats (8.26 vs 9.03 for non-diabetic rats). It is concluded that diabetes reduces the sensitivity of aortic tissue to nifedipine and may affect the stimulation-contraction coupling of vascular smooth muscle in such a way that a higher influx of calcium results after stimulation and that this may be responsible for diabetes-induced vascular complications. The present study was carried out to investigate the changes brought about by diabetes in the calcium influx, contractile responses of the aorta and inhibitory effect of nifedipine to shed some light on the mechanism of vascular damage seen in diabetic patients. In this study streptozotocin-treated rats were used as an experimental model of diabetes, since it has been reported that intravenous (i.v.) injection of this compound destroys the beta-cells of the pancreas, producing an insulin-dependent diabetes [3].