Localization of the metabolic processes affected by calcium during corticotropin action

To define the role of calcium during corticotropin-induced steroidogenesis, adrenal sections were incubated under conditions of varying degrees of calcium depletion. Corticosterone production, [14C]leucine incorporation into protein, and tissue cyclic AMP levels were measured concomitantly. Omitting calcium from the incubation media inhibited all three processes to variable extents, thus limiting conclusions regarding which process is most dependent on calcium. While calcium was required during the early phase of corticotropin action, it was not required during later phases: rapid induction of calcium deficiency did not diminish the heightened rate of steroidogenesis previously induced by corticotropin in the presence of calcium. Thus, while calcium is required for induction of steroidogenesis factor(s), the operation of the latter is not dependent upon calcium in the extracellular fluid.