Immunohistochemical localization of 3β-hydroxysteroid/Δ5-Δ4-isomerase, tyrosine hydroxylase and phenylethanolamine N-methyl transferase in adrenal glands of sheep fetuses throughout gestation and in neonates
Summary. Immunoreactive 3β-hydroxysteroid dehydrogenase/Δ5-Δ4-isomerase (3β-HSD) was localized in adrenal glands of sheep fetuses in cortical-type cells, but not in medullary-type cells, from day 43 of gestation to term and in 2–4-day-old neonates. From day 54 of gestation, the formation of distinct zones within the adrenal cortex was apparent and immunoreactive 3β-HSD was found in cortical cells in the zona fasciculata and in groups and cords of cortical cells within the developing medulla, with weak positive staining in the zona glomerulosa. At this stage, most medullary cells were positive for immunoreactive tyrosine hydroxylase, and some of these cells with a juxta-cortical distribution also stained positively for immunoreactive phenylethanolamine N-methyl transferase (PNMT). Between days 65 and 130, the adrenal medulla increased in size with little change in the width of the cortex. Organization and zonation of immunoreactive 3β-HSD staining cells were evident in the zona fasciculata and in groups of cells in the medulla. Between day 130 and term, uniform immunoreactive 3β-HSD staining was found throughout the zona fasciculata, and there was also staining in single cells and small clusters of cells throughout the medulla. At this stage, immunoreactive tyrosine hydroxylase was distributed in most cells throughout the medulla, but in two distinct patterns: cells staining intensely for immunoreactive tyrosine hydroxylase in the central region of the medulla, and cells exhibiting weaker staining for immunoreactive tyrosine hydroxylase localized in a juxta-cortical position. These juxta-cortical cells were also positive for immunoreactive PNMT. Similar patterns of immunoreactive 3β-HSD, tyrosine hydroxylase and PNMT staining were found in 2–4-day-old neonates. We conclude that immunoreactive 3β-HSD is present in adrenal glands of sheep fetuses throughout gestation and in neonates, that progressive organization of cells containing 3β-HSD to form the fetal adrenal cortex occurs during gestation, and that immunoreactive 3β-HSD-positive cells may be closely associated with catecholamine biosynthesizing medullary cells during fetal life.