Two Independent Effects of Cortisol on Chicken Liver

Activities of two key enzymes of glycogen metabolism have been measured after an acute administration of cortisol to 3d-old chickens. Glycogen synthase activity is enhanced 2-3 hours after a cortisol injection, and this activation is blocked by use of protein synthesis inhibitors. Glycogen phosphorylase activity is enhanced at an early stage, and this effect is not suppressed by protein synthesis inhibitors. Liver cAMP levels are not increased concomitantly with this early activation of glycogen phosphorylase; indeed they are depleted. These results point to the existence of an effect of cortisol previous to and independent of its nuclear interaction, and not mediated by an activation of the membrane adenylate cyclase.