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 KCl-induced contraction of the arorta in diabetic rats was reduced by 38%, but the EC50 of KCl remained unchanged. The pA2 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.