Cortisol production by cells isolated from the outer and inner zones of the adrenal cortex of the guinea pig.

Cortisol production by cells isolated from the outer (glomerulosa and fasciculata) and inner (reticularis) zones of the adrenal cortex of the guinea pig was evaluated in order to clarify the steroidogenic function of the zona reticularis. Basal cortisol production by the outer zone cells was 5-10 times greater than that by the inner zone cells. Cells from the outer zone increased cortisol production in response to ACTH (ED50, approximately 33 pg/ml), while cells from the inner zone failed to respond to ACTH. Likewise, cells from the outer zone increased cortisol production in response to (Bu)2cAMP, while cells from the inner zone failed to respond. When either pregnenolone or progesterone was added to the incubation mixture, an increase in cortisol production by cells of the inner zone was noted, although the increase was significantly less than that observed for cells from the outer zone. These results suggest that the zona reticularis of the guinea pig adrenal ordinarily produces little or no cortisol, although the enzyme machinery is present and capable of producing a limited amount of cortisol when supplied with the appropriate precursor.