Electron microscopic study of the response of the adrenocortical X-zone in mice treated with sex steroids.

In the adrenal cortex of 23- to 27-day-old C3H/Tw female mice, the eosinophilic X-zone became increasingly increasingly undetectable after 3 injections of 100 microgram testosterone propionate (TP). Whorls of smooth endoplasmic reticulum (sER) and peculiar complexes of mitochondria and sER, characteristics of X-zone cell, were no longer present in mice given 7 daily injections of TP. The ordinary mitochondria, although reduced in number, became swollen and actually increased in percent area occupied. They had well-developed tubulovesicular cristae. The lipid droplets increased in size and number after 3 daily TP injections, but decreased after 7 daily injections. Rough endoplasmic reticulum and sER were reduced in area in mice receiving 7 daily injections. The X-zone also became indistinguishable from the zona fasciculata after 7 daily injections of 5alpha-dihydrotestosterone propionate. Injections of progesterone or estradiol-17 beta had no effect on the X-zone.