Prenatal and postnatal ovine adrenal cell responses to prostaglandin E(2)

To examine the secretory effect of prostaglandin E(2) (PGE(2)) and ACTH on the adrenal glands of prenatal and postnatal sheep.

Immunocytochemistry was used to examine the adrenal cortex and medulla for 17alpha-hydroxylase and tyrosine hydroxylase immunoreactivity. Microphysiometric technique was used to measure [H(+)] after exposure of whole dispersed prenatal and postnatal adrenal glands to PGE(2), ACTH, or both.

Immunocytochemistry showed many cortical-type cells in all adrenal medullae and many medullary-type cells in fetal adrenal cortices. Maximum H(+) responsiveness to PGE(2) decreased with increasing age. The developmental age-related pattern of maximum percentage change in [H(+)] during ACTH exposure was similar to previous findings with cortisol production as the endpoint. ACTH stimulated H(+) production at 80 days' gestation and at all ages greater than 125 days' gestation (P <.05). The molar concentration of ligand required to elicit a response that was 50% of maximum response (EC(50)) for the ACTH response was lower in fetuses than in newborn lambs (<1 day and 3 days old), but there was no change in EC(50) for PGE(2) across the ages studied. Adrenal cell response to ACTH after prior ACTH and PGE(2) exposure was higher (P <.05) compared with ACTH after ACTH or ACTH alone at 110 days' gestation only and was lower in 3-day-old lambs.

Based on the ACTH results, microphysiometry was a valid method for investigating dispersed adrenal cell physiology. Prostaglandin E(2) stimulated dispersed adrenal cells during the mid-gestation ACTH refractory period, but this effect decreased with increasing age. Prostaglandin E(2) sensitized adrenal cells to ACTH at 110 days' gestation but inhibited ACTH effects at postnatal day 3.