Steroid metabolism in the testes of the African catfish, Clarias gariepinus (Burchell), during spawning season, under natural conditions and kept in ponds.

Steroid metabolism in the testes of Clarias gariepinus, collected in the Hula nature reserve and a fish pond in North Israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3H]pregnenolone or [3H]androstenedione as precursors. It could be demonstrated that [3H]pregnenolone was mainly converted via progesterone and 17 alpha-hydroxyprogesterone into androstenedione, 11 beta-hydroxyandrostenedione, and 11 beta-hydroxytestosterone. The final products from [3H]androstenedione incubations, 11 beta-hydroxyandrostenedione, and 11 beta-hydroxytestosterone, confirm these findings. The major difference in steroid metabolism between wild and pond animals was a reduction in androgen synthesis in the first group, resulting in higher amounts of C21-steroids. Moreover, the synthesis of two steroid esters, including pregnenolone ester, could be established with tissue incubations of wild animals only. Steroid conjugates were hardly synthesized at all in the testes of C. gariepinus.