Abstract
Castrated adult male C57 BL/6J mice displayed a wide perimedullary zone (secondary X-zone) whose cells were characterized by proliferated rough and smooth endoplasmic reticulum and elongated mitochondria with lamellar cristae. Castrated mice which received 0.08 mg/g of cyproterone acctate showed a much inhibited secondary X-zone at the light microscopic level, while at the ultrastructural level the perimedullary cells lacked the proliferated rough and smooth endoplasmic reticulum as well as the elongated mitochondria. Cyproterone acetate may inhibit the steroidogenic parameters of the androgen-producing cell population of the adrenal cortex without testicular mediation.