Inhibition of pituitary gonadotrophic activity in the viviparous seaperch Cymatogaster aggregata Gibbons by a dithiocarbamoylhydrazine derivative (I.C.I. 33 828).

Abstract

A suspension of Methallibure (I.C.I. Compound 33 828) was added regularly for about 6 weeks to aquaria housing males of the teleost Cymatogaster aggregata. The testis atrophied and the gametogenetic processes of maturation were suspended. Histochemically demonstrable 3β-hydroxysteroid dehydrogenase and sudanophilic lipids diminished and the interstitial cells of Leydig regressed. At the end of the experiments the fleshy modifications on the male anal fin (secondary sex structures which develop under the influence of male gonadal hormones) were in a state characteristic of immature fish. Methallibure treatment resulted in these changes, which were characteristic of hypophysectomy, without the marked antithyroid activity histologically evident in thiourea treatment. All thiourea-treated and control animals remained in breeding condition. It is concluded that the addition of Methallibure to the aquarium water will directly block the production and (or) release of pituitary gonadotropins and thus inhibit spermatogenesis and testicular steroidogenesis.