Ontogeny of catecholamine-synthesizing enzymes and enkephalins in the sheep adrenal medulla: an immunocytochemical study.

An immunocytochemical staining technique was used to investigate the development of the sheep adrenal medullary cells containing enkephalins and the catecholamine synthetic enzymes dopamine beta-hydroxylase (DBH) and phenylethanolamine N-methyl transferase (PNMT). No staining was observed in the adrenocortical cells with any of the antisera used in this study. Positive staining with anti-DBH was observed throughout the medulla in both adult and fetal adrenal glands from 80 days of gestation. Positive staining with anti-PNMT was observed in all glands from as early as 80 days of gestation, and staining with this antiserum was mainly confined to the peripheral medullary cells, which were adjacent to, and interdigitated between, the cells of the adrenal cortex. In the fetus between 80 and 120 days of gestation, staining for the enkephalins was observed in both the peripheral columnar and the central polygonal adrenal medullary cells. After 125 days of gestation and in the adult ewe, the peripheral columnar cells were uniformly stained with anti-enkephalin whereas many unstained cells were present in the central medullary region. Therefore, enkephalin-containing peptides are present in the catecholamine cells of the fetal and adult sheep adrenal and there appears to be a changing pattern in the distribution of the enkephalins in the fetal adrenal in late gestation.