Dissociated Response of the Epithelium of the Rabbit Oviduct to Estrogen1

The estrogen-induced regeneration of the oviduct epithelium of the castrate rabbit was studied with the colchicine technique. A descending caudad gradient of mitotic responsiveness to estradiol was noted. Proliferation of the oviduct epithelium began 1 day after that in the uterine epithelium but took place simultaneously with that of the vagina. However, the mitotic frequency was much lower in the oviduct than in the other epithelia of the genital tract. Within the oviduct mitosis was most evident in the infundibulum and upper ampulla. The lower ampulla and isthmus differed from the other parts of the oviduct by exhibiting a lower mitotic frequency and by responding later to the stimulatory action of estrogen. The lower sensitivity and delayed response to the action of estrogen of the lower ampulla and isthmus over that of the infundibulum and upper ampulla may have a wider implication in the reproductive process. The adaptation of the oviduct activities to the demands of the migrating zygote may be facilitated by similar differences in the response to changes in the hormonal balance.