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

Steroid metabolism in the seminal vesicles of Clarias gariepinus, collected in the Hula nature reserve and in a fish pond in North Israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3H]pregnenolone, [3H]dehydroepiandrosterone, or [3H]androstenedione as precursor. The seminal vesicles were able to synthesize androgens, 11-oxygenated androgens, and 5 beta-reduced C19- and C21-steroids; a pregnenolone ester was also formed. Furthermore a potent synthesis of steroid glucuronides, i.e., the glucuronides of testosterone, 5 beta-dihydrotestosterone, 5 beta-androstan-3 alpha, 17 beta-diol, and etiocholanolone, was observed. When reared in ponds, the African catfish fails to spawn. This might be caused by a change in steroid glucuronide (pheromone) production by the seminal vesicles, as it appeared that the synthesis of glucuronides differs in "wild" and "pond" animals. Etiocholanolone glucuronide is completely absent in pond animals.