Sex differences in adrenocortical structure and function. XXI. The effects of gonadectomy and testosterone or estradiol replacement on mitotic activity of the rat adrenal cortex.

The study was designed to investigate the mitotic activity of adrenal cortex in the adult male and female rats and to explain the effects of gonadal hormones on proliferation of rat adrenocortical cells. Mitotic index in individual zones of the adrenal cortex as well as a total number of mitoses on the "equatorial" sections of the gland were estimated in dexamethasone and colchicine pretreated control, gonadectomized and gonadectomized-gonadal hormone replaced rats. If compared with males, mitotic index of the zona reticularis (ZR) cells was higher in females, however, there was no difference in the remaining zones of the cortex. Neither orchiectomy nor testosterone had an effect on mitotic index of the zona glomerulosa (ZG) and zona fasciculata (ZF) cells. In the ZR, orchiectomy increased this index, an effect reversed by testosterone. Neither ovariectomy nor estradiol administration had an effect on mitotic index of the ZG and ZF, while in the ZR estradiol lowered this index if compared with control and gonadectomized rats. Total number of mitoses per "equatorial" section of the gland was similar in male and female rats. Orchiectomy increased this value, an effect reversed by testosterone. On the other hand, neither ovariectomy nor estradiol had an effect on the total number of mitoses per section of the adrenal gland.