Submicroscopic Study of the Pituitary Action on the Adrenocortex of the Rat

Abstract

The effects of hypophysectomy and of restitutional therapy with ACTH on the fine structure of the rat adrenal cortex were studied with the electron microscope. During the first week after hypophysectomy the only change was the lack of protruding mitochondrial vesicles frequently observed in the normal fasciculata and reticularis. After two weeks there are marked changes in the mitochondria of the outer fasciculata consisting in the modification of the normal vesicular pattern that leads to the appearance of tubulovesicular elements and convoluted tubules. At the same time the relative proportion of mitochondrial matrix increases. In more advanced stages mitochondria contain a few straight tubuli and assume a pattern similar to that found in the normal glomerulosa. In the inner zones the predominant changes consist in degeneration and atrophy. With time the lipid droplets of the entire gland become dissolved during the preparation of the material. The glomerular cells show no marked changes with hypophysectomy. The injection of ACTH after hypophysectomy produce changes in the mitochondria with surface openings and vesiculation into the hyaloplasm. Several injections are needed to have a restoration of the normal structure of the fasciculata. These results are discussed in relation to the concepts of ultrastructural zonation. It is further suggested that the action of ACTH on adrenal secretion could be associated with the formation and transfer of mitochondrial vesicles into the hyaloplasm. This effect may lead to the functional integration of the cellular compartments involved in the secretory process.