Steroid production in testicular tissue of the European eel

Testicular tissue of normal and hCG-stimulated European eels was incubated in vitro with tritiated progesterone or androstenedione as substrates. The following compounds were isolated and identified: 5 beta-androstane-3,17-dione; 17 beta-hydroxy-5 beta-androstan-3-one; androst-4-ene-3,11,17-trione (adrenosterone); 11 beta-hydroxyandrost-4-ene-3,17-dione; 11 beta-hydroxytestosterone; 3 alpha,11 beta-dihydroxy-5 beta-androstan-17-one, and an additional steroid for which the oxidation product was identified as 5 beta-androstene-3,11,17-trione. Four of these steroids have not been hitherto identified in gonadal tissue of any vertebrate. The pattern of steroid production in this tissue is unique for its 5 beta-reduction, for the appearance of adrenosterone as a major metabolite, and for the lack of production of 11-ketotestosterone, which is a regular metabolite of gonadal tissue of teleosts. Thus, it appears that steroid metabolism in the eel testis deviates considerably from the known pattern of steroid production in gonads of other vertebrates.