The existence of an early effect of testosterone, prior to the effects dependent upon interaction between the hormone-citosolic receptor complex and the cellular nucleus, has been explored in the present paper, in 3-day old chickens. Liver glycogen phosphorylase activity is increased before protein synthesis activation, and furthermore this effect is not blocked by antibiotics (actinomicin D and cycloheximide) inhibitor of protein synthesis. When liver phosphorylase is activated, cAMP levels are not enhanced, as would be expected, but deeply depleted. The hypothesis of a phosphorylase-kinase activation due to an increase in the intracellular Ca++ concentration is considered.

Cortisol produces a glycogenogenic effect 5 hours after intraperitoneal injection to 3 day old chicks. This effect is dependent on protein synthesis because it can be blocked by antibiotics such as actinomycin D. On the other hand, there is a previous glycogenolytic effect 45 minutes after cortisol administration which is independent of protein synthesis. Thyroid hormones produce a similar early effect as has been previously shown. However, the observed glycogenolysis after cortisol injection is not correlated with an enhancement in the liver cAMP levels.

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.

Activities of hepatic glycogen synthase a and glycogen phosphorylase a have been studied in mouse liver at different times after an acute intraperitoneal administration of hydrocortisone. It has been observed an increase of glycogen synthase a activity and a decrease of glycogen phosphorylase a between 2 and 3.5 hours after cortisol injection. An early effect, previous to the synthase activation has been discovered. Cortisol caused an increase of glycogen phosphorylase a activity in mice 45 min after injection. This early effect of cortisol is independent of protein synthesis and it does not imply an increase in cAMP levels.

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