The ultrastructure of the adrenal cortex of the rat under normal and experimental conditions

Abstract

The adrenal glands of rats were fixed by intra-arterial perfusion of glutaraldehyde and osmium tetroxide under normal conditions and after short-term administrations of Dexamethasone (a synthetic glucocorticoid) and adrenocorticotropic hormone (ACTH). Sections of the entire cortex and part of the medulla were analyzed in the electron microscope at magnifications ranging between 200 × and 60 000 ×. This allowed for great accuracy in identifying the zones of the cortex. In all cases, blood vessels and sinusoids remained open and the fenestrated endothelium was well preserved throughout the cortex and the medulla. The parenchymal cells were also well preserved, including those of the zona reticularis, and signs of cell death were no more common in one or the other zone. The mechanism of accumulation and depletion of lipid droplets was studied, particularly in the zona fasciculata. Under the influence of Dexamethasone, lipid droplets accumulated in large numbers 25 hours after administration. The ACTH effect was evidenced 10 minutes after injection by a disappearance of lipid droplets and by a reduced amount of smooth endoplasmic reticulum. The lipid droplets appeared to arise either from the smooth endoplasmic reticulum or from Golgi elements. As the droplets enlarged, they became surrounded by an increasing number of profiles of smooth endoplasmic reticulum. The profiles merged to form a continuous membranous casing near the boundary membrane of the droplet. As a final step, the peripheral part of the membranous casing fused with the surface membrane of the cell. The content of the lipid droplet was discharged into the subendothelial space together with the boundary membrane and the central part of the casing of the smooth endoplasmic reticulum. A membranous ghost remained temporarily. It is proposed that this represents the elaboration and release of corticosteroid hormones by a modified apocrine secretion which we would term endoplasmocrine secretion for the purposes of satisfactorily distinguishing it from other modes of endocrine and exocrine secretion.