Influences of Corticosteroids on Cardiac Glycogen Concentration in the Rat

Abstract

Bilateral adrenalectomy resulted in a decrease (4.97 to 2.79 mg/g) in cardiac glycogen concentration in pentobarbital-anesthetized rats. Similar differences were observed at 10 to 14 days and at 27 days after adrenalectomy. Sham-adrenalectomized rats had normal cardiac glycogen concentration (4.98 mg/g). Total phosphorylase and phosphorylase α activities and glucose-6-phosphate concentrations in hearts obtained from adrenalectomized rats were not significantly different from controls. Total glycogen transferase activity was decreased in adrenalectomized rats and for any given glycogen concentration, the percent of the glycogen transferase in the independent form (percent transferase I) was significantly lower in the adrenalectomized rats than in the intact controls. The glucocorticoid dexamethasone (40 µg/day) prevented the decreases in cardiac glycogen concentration and percent transferase I in adrenalectomized rats. In the intact rat dexamethasone (40 µg/day) increased cardiac glycogen concentration and total transferase activity to above control levels as did larger doses in both adrenalectomized and control rats. The mineralocorticoid deoxycorticosterone acetate (DOCA), had relatively little effect on cardiac glycogen concentration. Conclusion: glucocorticoids exert a regulatory role in cardiac glycogen metabolism.