Biological evaluation of two estrogenic steroids as possible rodent chemosterilants.

To determine their suitabilities as rodent chemosterilants the effects of W3566 an estrogenic steroid and mestranol were compared in the laboratory albino rat in 4 biological parameters: 1) prolonged estrogenic response 2) prolonged inhibilition of fertility 3) termination of pregnancy and 4) the effect on offspring after treatment of lactating mothers. Single oral doses (10-10000 mcg) of W3566 showed more prolonged and intense estrogenic activity than similar doses of mestranol. As a potential rodent chemosterilant W3566 seems a better choice since prolonged activity helps ease the problems of repetitive dosing in bait.