Seasonal changes in steroid metabolism in the male reproductive organ-system of the African catfish, Clarias gariepinus

Abstract

Steroid and steroid glucuronide synthesis in feral male African catfish was investigated in vitro by incubating testes with [3H]-pregnenolone and seminal vesicles with [3H]-androstenedione. In testes, the capacity to form progestins, androgens, especially 11-oxygenated ones, and steroid glucuronides increased enormously in the periods of full spermatogenesis and breeding, with 5β-pregnane-3α,17α,20α-triol and 5β-pregnane-3α,17α-diol-20-one glucuronide as the main polar products. In the same periods, seminal vesicles are able to form 11-oxygenated androgens from [3H]-androstenedione and show an increased capacity to form testosterone. Their ability to produce testosterone glucuronide is strongly enhanced in the period of full spermatogenesis and further increases in the breeding period. In this latter period, the capacity to form 5β-androstane-3α,17α-diol glucuronide is also stimulated. The function of the main steroids and steroid glucuronides is discussed, with special reference to the water-soluble compounds that may serve as sex pheromones.