Studies on the Mode of Action of Glucocorticoids in Rats: A Comparison of the Effects of Cortisol and Glucose on the Formation of Liver Glycogen

Five rats from a group of adrenalectomized, fasted rats were given a single injection of approximately 1 mg cortisol/100 g body weight, after which blood glucose levels were measured at intervals over a period of 3 hours. Another 5 rats from the same group were given a series of subcutaneous injections of glucose during the 3-hr period, and their levels of blood glucose were measured at similar intervals. At the end of the 3 hours, liver glycogen was determined. Although the average blood glucose levels of the glucose-injected group were higher throughout the experiment than those of the cortisol-injected group, the cortisol-injected rats were found to have considerably more glycogen. The conclusion is drawn that the early changes in liver glycogen resulting from the injection of cortisol in fasted, adrenalectomized rats cannot be accounted for quantitatively by changes in blood glucose levels alone.