Adenylate cyclase activity and cyclic AMP production in the outer and inner zones of the adrenal cortex.

It has been reported that cells isolated from the inner zone of the guinea pig adrenal cortex fail to have a steroidogenic response to ACTH. To further explore this, adenylate cyclase activity of membrane particles and cAMP production by cells prepared from the inner and outer adrenocortical zones were determined. The cAMP response to ACTH and forskolin was similar for cells from both zones. Basal adenylate cyclase activity was significantly higher in the inner zone; and while absolute responses to ACTH, GppNHp, GTP, NaF, and forskolin were greater for the inner zone, relative responses were similar for the two zones. These observations suggest that the inner zone of the guinea pig adrenal cortex may have a defect in ACTH action at a step(s) beyond cAMP formation.