[Cyclic AMP-dependent and -independent protein kinases in the adrenal cortex]

The various protein kinase activities characterized in adrenal cortex from different mammalian species do not differ in their molecular and catalytic properties from similar types of enzymes described in other tissues. The cyclic AMP-dependent system has been the most thoroughly investigated in adrenocortical tissue and is generally accepted as an obligatory intermediate in the intracellular response to ACTH action. In addition, adrenocortical cells contain two types of messenger independent protein kinases, one of which being selectively activated by polyamines in vitro and possibly related to the control of adrenocortical growth processes. The definition of intracellular phosphorylatable targets related to specific adrenocortical functions might have been obscured by the pleiotypic effects displayed by ACTH, the major effector of these cell activities. Cholesterol esterase appears one of these targets and 11 beta-hydroxylase cytochrome P-450 has been found activated in vitro by a cAMP dependent process. Future research should provide a better understanding of the role of protein phosphorylation-dephosphorylation processes as a regulatory device in adrenocortical cell functions. This includes possible complex modulation by multisite phosphorylations of a given target protein, involving several different protein kinase systems under the dependence of separate intracellular effectors.