Testosterone metabolism in the olfactory epithelium of intact and castrated male rats.

To study the ability of the olfactory epithelium (OE) to transform testosterone (T) into its active metabolites estradiol (E2) and dihydrotestosterone (DHT), and the influence of castration on this ability, 24 adult male rats were either castrated, and subsequently treated with oil or T, or sham operated. In all groups the in vitro conversion of T by the OE into E2 and DHT is relevant, demonstrating for the first time the presence of aromatase and of 5 alpha-reductase in this tissue. In particular conversion of T into E2 is lowered by castration and restored by T replacement, suggesting that aromatization in this tissue is androgen dependent. The ability of circulating T to influence morphological and physiological features of the OE suggests the hypothesis that androgens may vary the functioning of the olfactory apparatus and modulate the efficiency by which olfactory information is conveyed to the brain.