In vivo upregulation of adipocyte alpha 2-adrenoceptors by androgens is consequence of direct action on fat cells

Adipose precursor cells from male hamsters were exposed to testosterone in primary culture. The effect of the sex steroid on alpha 2-adrenoceptor (AR) expression was studied. Testosterone enhanced alpha 2-AR expression during adipose conversion to an identical extent to that determined in vivo without modification of the differentiation state as estimated by glycerol-3-phosphate dehydrogenase activity. The expression of preadipocyte alha 2-ARs from female hamster was also submitted to the testosterone control. The upregulating effect was androgen specific, since only testosterone and dihydrotestosterone were efficient in inducing an increase of alpha 2-AR density, whereas estradiol, dexamethasone, progesterone, and androstenedione were without any action. To conclude, androgens act directly on fat cells by upregulating alpha 2-AR expression. The effects are not mediated by aromatization into estrogens and probably involve androgen receptor interactions.