In contrast to the regulation of hormone secretion in peptide-secreting cells, in which both release and synthesis are important variables, the regulation of steroid secretion requires only an assessment of (those factors╖ controlling synthesis. In most steroid-secreting tissues, this process is relatively unн complicated with one or two factors usually regulating.: the biosynthetic processes. The single exception is the regulation of aldosterone secretion. Not only are there perhaps more than a dozen factors involved, burthese factors exert their effects through potentially all proposed transduction mechanIsms, except direct activation of a tyrosine kinase. The mechanisms utilized by the glomerulosa cell include:(a) cyclic AMP formation;(b) regulation of cytosolн ic free calcium and protein kinase C activity through the phosphatidylinositol system;(c) cytosolic GMP formation;(d) ion channel and modification; and (e) modification of the membrane potential. Most if not all of these transducн tion mechanisms create an environment in which phosphorylation of a variety of intracellular proteins is increased. Presumably it is this increased phosphorylation that leads to a change in steroid enzyme activity and aldosteн rone secretion. The input from each of these transduction mechanisms is probably integrated, although the mechanism of this integration is obscure.