Methallibure studies on tilapia. III. Effects of tilapian partially purified pituitary gonadotrophic fractions on the testes of Methallibure-treated Sarotherodon spirulus (= Tilapia nigra)

Tilapian fish Sarotherodon spirulus (= Tilapia nigra) were treated with the gonadotrophic inhibitor, methallibure, for 9 weeks during the last 2 of which they were divided into a control group and 8 experimental groups. They were given thrice weekly intraperitoneal injections on alternate days for 2 weeks of one of the following: deionized water, 5 or 50 μg of tilapia pituitary homogenate (TPH), 5 or 50 μg of tilapia pituitary glycoprotein fraction (T-GTN), tilapia pituitary glycoprotein CM-cellulose fraction 1 (T-CM-1) or of fraction 2 (T-CM-2) in 0.1 ml of deionized water in the eight respective experimental groups. TPH and all the fractions contained some gonadotrophic activity and induced testicular and Gonosomatic Index (GSI) elevation with at least the higher dose level. The most comprehensive effects were induced by T-GTN and T-CM-1 which were apparently equally effective using all the parameters so far examined. The T-CM-2 high dose was only as effective as the lower dose of either T-GTN or T-CM-1 suggesting that the purification process concentrated most of the gonadotrophic activity into the T-CM-1 fraction. In higher vertebrates, the same purification procedure leads to the concentration of FSH and LH in the CM-1 and CM-2 fractions, respectively.