Failure of Castration to Modify Estradiol-Induced Tube-Locking of Rabbit Ova

Exogenous estradiol, administered in the appropriate dose at the proper time in relation to ovulation, “locks” ova within the rabbit oviduct. The mechanism by which estrogen acts on the oviduct has not been elucidated. In these experiments, ovaries were removed from rabbits at various times prior to the transfer of donor ova and the administration of estrogen. The significant number of ova remaining in the oviducts 72 hours later demonstrates that ovaries are not essential to estrogen-induced “tube-locking.”