Endocrine Abstracts

In the Saharan gerbil Meriones libycus, live trapped in the south west of Algeria, castration, carried out during the breeding season (Winter–Spring), induced, 50 days later, important modifications in adrenal gland activity. The adrenal weight and cortex volume increased by 11.7% and 25.0% respectively, with hypertrophy of reticularis zona (+57%, P<0.001) and hypotrophy of fasciculata zona (−13.4%, P<0.001) while glomerulosa exhibited only small height variations. However, the histological study showed significant increases in cellular height and nucleus diameter of reticularis cells. In the fasciculata zona, the height cells also increased (11.4%; P=0.04) whereas nucleus diameter decreased by 11% (P=0.003). On the other hand, adrenal content of cortisol decreased by 30% (absolute values; P=0.4) or 50% (relatively to adrenal or body weights; P=0.2). Plasma cortisol also decreased (−83%, P=0.3) in the castrated males.

Testosterone replacement was performed by twice daily of s. c. injections of 75 μg sesame oil diluted testosterone enanthate, during 7 days in both 50 days castrated gerbils during breeding season and intact animals during resting season (autumn). This treatment induced adrenal hypertrophy due to that of cortex volume and fasciculata and reticularis zona in all testosterone treated animals. However, the adrenal cortisol content increased in all animals, whereas plasma cortisol values were restored in castrated ones (breeding season) and continue to decrease in non castrated (non breeding season).

This study suggests that testosterone affects the adrenal structure and activity, particularly in cortisol production by inhibiting or stimulating its secretion either directly via androgen receptor or via hypothalamic–pituitary–adrenal axis. Then, testicular androgens seemed to be implicated, at least in part, in the endogenous determinism of annual cycle of adrenal activity in this desert species.