MAINTENANCE OF PREGNANCY IN INTACT RABBITS IN THE ABSENCE OF CORPORA LUTEA1

Abstract

IT IS well known that the secretion of the corpus luteum, progesterone, plays an important part in the proliferation of the uterine endometrium, the growth and implantation of the ovum, the formation of the placenta, and the maintenance of pregnancy. In the rabbit, removal of the corpora lutea interrupts pregnancy while the administration of luteal extract (or progesterone) maintains gestation right up to the full term in the ovariectomized animals (Allen and Corner, 1929). Whether or not pregnancy can be maintained in an intact, non-ovulated animal by the administration of progesterone has not previously been determined. The possibility of such maintenance can be only investigated by transferring fertilized ova into a non-ovulated animal. In a previous investigation on the development of transferred rabbit ova in relation to the ovulation time of the recipient rabbits (Chang, 1950b), it was observed that ova at different stages (1 to 6 days after mating) could develop into normal young only