Varying the duration of A23187 administration alters its effect on adrenal steroidogenesis.

A variety of effects of A23187 have been reported as its actions on adrenocortical steroidogenesis. This diversity probably resulted because of differences in the protocol of applying the Ca++ ionophore. We continue to observe a dose-dependent potentiation by the ionophore on ACTH-stimulated corticosterone secretory activity of superfused rat adrenocortical slices. This effect was eliminated or reversed if the tissue was pretreated with A23187 for 30 min prior to secretagogue application. The quality of the ionophore effect also depends on the submaximal dose of ACTH employed.