Hyperglycemic action of zinc in rats.

The effect of zinc on serum glucose, insulin and glucagon as well as liver glycogen was investigated in normal, adrenalectomized (ADX), and diabetic rats. Serum glucose was significantly elevated within 15 minutes after intraperitoneal administration of zinc (25 mumol) but returned to normal limits within 4 hours. Similar effects on serum glucose were noted with orally administered zinc. Significant depletion of hepatic glycogen in zinc-treated rats suggests glycogenolysis was responsible at least in part for the increased blood glucose. Adrenalectomy completely eliminated the hyperglycemic response to this metal, whereas adrenergic blockade with phenoxybenzamine and propranolol was effective in preventing hyperglycemia. The hyperglycemic response to zinc was not eliminated in diabetic rats. Administration of dexamethasone, alone or in combination with zinc, was unable to change serum glucose concentrations in ADX rats. Plasma glucagon was significantly elevated within 15 minutes but was reduced 6 hours after zinc treatment. Insulin was significantly depressed within 30 minutes after administration of zinc and eventually increased over controls by 4 hours after treatment. These data suggest that the hyperglycemic response to zinc depends on a mechanism, requiring an intact adrenal gland, which acts to produce a rapid alteration in blood glucose.