Evidence that long-term administration of a methionine-enkephalin analogue stimulates the growth and steroidogenic capacity of rat inner adrenocortical cells.

A prolonged infusion with D-ala2-met-enkephalinamide (DALA) caused a significant increase in both basal and ACTH-stimulated corticosterone secretion by dispersed inner adrenocortical cells of rats whose hypothalamo-hypophyseal axis was pharmacologically interrupted. This effect of DALA was associated with a notable hypertrophy of isolated cells. These findings suggest that enkephalins are involved in the stimulation of the growth and steroidogenic capacity of the cells of the inner layers of rat adrenal cortex.