Effects of Adrenocortical Steroids on Carbohydrate Metabolism in Hypophysectomized Dogs; Studies With C14-Labeled Glucose

Abstract

Hypophysectomized dogs exhibit severe disturbances in carbohydrate metabolism and in recent studies using C14 glucose it was shown that such dogs have a) smaller than normal body glucose pools and b) lower rates of glucose inflow into the plasma from the liver and glucose uptake from the plasma by the tissues. These dogs also have lower rates of total CO2 production. Since cortisone or hydrocortisone treatment ameliorates various abnormalities of carbohydrate metabolism in hypophysectomized animals, the effect of a steroid regimen (0.8–1.5 mg/kg/day for 8–16 days) on several parameters was studied in hypophysectomized dogs. Using the C14 glucose-dilution technique it was found that the steroid treatment resulted in a) an increment in body glucose pool size proportional to the simultaneously observed increase in plasma glucose concentration and, b) an increase in the rate of glucose output by the liver and glucose uptake by the tissues. The rate of total CO2 production was not altered by the steroid treatment. The untreated hypophysectomized dog, in contrast to the normal one, is unable to increase adequately glucose output by the liver in response to hypoglycemia resulting from an insulin-induced increase in plasma glucose uptake by the tissues. It is reasoned that the steroid treatment brings about an increased turnover of plasma glucose by a primary increase in the release of glucose by the liver, rather than by a primary increase in glucose uptake by the tissues. An increase in endogenous insulin secretion, brought about by the increased glucose release, could explain the increased glucose uptake by the tissues.