In vitro metabolism of steroid hormones in the liver and in blood cells of male rainbow trout (Salmo gairdneri Richardson)

Male rainbow trout show high plasma androgen levels beginning with the period of full spermatogenesis until the end of spermiation. The difficulties in explaining the steroid levels in regard to the concomitant changes of the plasma GTH concentrations prompted investigations into whether the steroid demand may be met in part by extragonadal steroid metabolism. The results of in vitro experiments with liver tissue fit into the concept of an interrenal-liver-gonad axis of androgen production, since increased amounts of C-19 steroids were detected in the media after incubation of hepatic tissue with cortisol. 17β-Hydroxysteroid dehydrogenase and hydroxysteroid glucuronyltransferase activities were shown to be associated with blood cells of mature males. The fact that unidentified products from incubations with 17β-estradiol, testosterone, and 17β-hydroxyprogesterone were also found suggests that other steroid metabolizing enzymes are also associated with blood cells. The possibility is discussed that, assuming the blood cell activities are relevant in vivo, a production of potent androgens or the formation of water soluble steroid derivatives could proceed in the blood (e.g., 11-ketoandrostenedione → 11-ketotestosterone; testosterone → testosterone glucuronide), possibly affecting the organism's steroid balance.