Transport of oestrogens in semen to the female rat during mating and its effect on fertility.

Available evidence (Greenwald, 1961; Emmens & Finn, 1962) shows that natural and synthetic oestrogens given to female rats alter ova transport and thus prevent pregnancy. Preliminary work in our laboratory showed that when oestrogens were administered to male rats which were then mated with normal females, pregnancy did not ensue. The present study was undertaken to in¬ vestigate the mechanism (s) responsible for the lack of fertility following oestrogen treatment of males. Sixty Sprague-Dawley males (278 to 350 g) which had mated the previous night were randomly divided into two equal groups and individually caged. Pre-treatment fertility was established by killing the bred females on Day 8 of pregnancy and checking for conceptus. One group of males was injected sub¬ cutaneously with 1-0 mg of oestradiol-17/? (in 0-5 ml of peanut oil) per rat daily for 8 days while controls received a like volume of oil. An oestrous female