Calcium channel blockers inhibit the hyperglycemic effect of calcitonin.

We studied the effect of Russian preparation of porcine calcitonin (calcitrin, 1 U/100 g) and blockers of Ca(2+) channels nifedipine (1 mg/kg, blocker of chemosensitive Ca(2+) channels) and isoptin (5 mg/kg, blocker of voltage-dependent Ca(2+) channels) on glucose metabolism. Calcitonin produced a pronounced hyperglycemic effect in rats. A close negative correlation was found between glucose level and total calcium content. Injection of calcitonin reduced glucose tolerance in rats. Isoptin and nifedipine reduced plasma calcium level and did not affect significantly the blood glucose levels, did not change the pattern of alimentary hyperglycemia in response to glucose load, completely abolished the hyperglycemic effect of calcitonin, and prevented calcitonin-induced impairment of glucose tolerance.