Steroidogenesis in pre- and postspawned ovaries of feral African catfish, Clarias gariepinus

Steroidogenesis in pre- and postspawned ovaries of Clarias gariepinus, collected in the Hula Nature Reserve in Israel, was studied following in vitro incubation with [ 3H] -pregnenolone or [ 3H] -androstenedione as precursors. In both experimental groups the ovaries synthesized progesterone, 17α-hydroxyprogesterone, 17α, 20β-dihydroxy-4-pregnen-3-one, androstenedione, testosterone, estrone, estradiol-17β, and several 5β-reduced C 21- and C 19-steroids. Testosterone and most of the 5β-reduced C 21- and C 19-steroids were also identified in a conjugated form as steroid glucuronides. In postspawned ovaries the production of these steroid glucuronides, especially testosterone-glucuronide and 5β-androstane-3α,17β-diol-glucuronide, and the steroid 5β-pregnane-3α,17α,20β-triol had increased significantly in comparison with prespawned ovaries. In these prespawned ovaries, on the other hand, androgen production, mainly testosterone, prevailed. It is suggested that the water-soluble compounds formed in relatively high amounts in postspawned ovaries are excreted into the external environment, where they may function as sex pheromones during the spawning period.