The occurrence and biosynthesis in vitro of 11-ketotestosterone in ovarian tissue of the mullet, Mugil capito, derived from two biotopes

Abstract

The concentration of 11-ketotestosterone in ovaries of the mullet, Mugil capito, confined to freshwater was by far greater than that found in ovaries of mullets derived from sea water. After incubation of androstenedione-7α- 3H with ovarian homogenates of mullets from both biotopes, testosterone and 11-ketotestosterone were identified as the main metabolites. The yields of these steroids were much higher in the incubation of ovarian tissue derived from fish confined to freshwater. The incubation products were identified by their mobilities on Celite partition chromatography columns, chemical characteristics in comparison with the corresponding authentic preparations, and finally, on the basis of constant specific activities throughout repeated crystallizations with respective reference preparations. The results obtained demonstrate the presence of 11-hydroxylase activity in the ovary of the mullet and also show that ecological differences may influence steroidogenesis in the ovary of the mullet. The relevance of these findings in explaining the lack of fecundity in mullets confined to freshwater is discussed.