An electron-microscopic study of the normal and stimulated adrenal cortex in the rat

Conclusion

Electron-microscopic studies of the adrenal cortex of normal rats and after ACTH administration and stress (induced by cold or formalin) had the following results:

• 1. In the capsular tissue, no special cells were found but fibroblasts. No specific cellular layers, named by some authors the transitional layers, were found.

• 2. The mitochondria of the adrenocortical cells were characterised by a honeycomb appearance in section, which is different from that of other cells. Small pores of the vascular endothelium were noted. An outflow of material through these pores suggests an interrelationship with the secretory mechanism, especially with the holocrine type of secretion. Besides mitochondria, in normal adrenocortical cells, the smooth surfaced variety of endoplasmic reticulum was found. Most of these elements are in the zona glomerulosa, less in the zona fasciculata and in the zona reticularis. No rough surfaced variety of endoplasmic reticulum was seen.

• 3. In the exhausted stage of severe stress, vacuole formation due to cytolysis was found. At the same time various organellae in the subendothelial space and in the vascular lumen were noted.

• 4. In adrenocortical cells in a hyperfunctional state, due to the administration of ACTH or stress induced by formalin (7 days), an increase of the smooth surfaced variety of endoplasmic reticulum and various vacuoles, and an appearance of granules of high electron density, as well as mitochondrial changes were observed.

• 5. Among morphological changes of the mitochondria, vacuolisation, deposition of substances, and vacuole formation due to the protrusion of the external membrane of the mitochondria were observed.

• 6. Granules of high electron density, presumably lipid, were found in the adrenocortical cells and classified into four types. Type I, small, compact granules of high electron density; Type II, small, empty granules; Type III, small, empty, multilobular granules; Type IV, large, compact granules of high electron density. Type I-granule was mainly found in zona glomerulosa and external layer of zona fasciculata. Type II- and III-granules were found in zona fasciculata. Type IV-granule was found in zona reticularis. Seldom different types of granules were found in one cell. The formation of granules has been discussed. These granules are considered to originate from the mitochondria themselves and from the vacuoles formed by the mitochondria.

• 7. The vacuoles in the adrenocortical cells are classified into three types, i.e. the genuine vacuole of normal adrenocortical cells, the functional vacuole connected with lipid hormone metabolism (vacuole formation within mitochondria and derived from the protrusion of the external membrane of mitochondria), and the degenerative vacuole produced by dissolution of cytoplasm (cytolysis).