Regulation of glycogenolysis in the liver of the newborn rat in vivo. Inhibitory effect of glucose.

Newborn rats were injected immediately after delivery with glucose or glucose plus mannoheptulose, and the time-courses of liver glycogen, plasma glucose insulin and glucagon concentration were studied. The administration of glucose prevented both liver glycogenolysis and the increase in plasma glucagon concentration, which normally occurs immediately after delivery. In addition, the administration of glucose prevented the decrease of plasma glucose and insulin concentration which normally occurs during the first hour of extrauterine life. Supplementation of glucose with mannoheptulose prevented the increase of plasma insulin concentrations caused by the administration of glucose; liver glycogenolysis, however, was not stimulated in these circumstances. The increase in the rate of glycogenolysis caused by the administration of glucagon was prevented in newborn rats previously treated with glucose. These results suggest that glucose exerts an inhibitory effect on the stimulation of neonatal liver glycogenolysis by glucagon.