Effects of ovariectomy or hypophysectomy on day one of pregnancy on development and transport of fertilized rat eggs.

Abstract

SUMMARY The development of fertilized eggs and their transport through the oviduct were studied in rats ovariectomized or hypophysectomized on day 1 of pregnancy. When killed on day 5 of pregnancy, 100%, 66% and 27% of the eggs were in the uterus of intact controls, ovariectomized and hypophysectomized rats, respectively. Thus both ovariectomy and hypophysectomy retarded transport of a proportion of the eggs. Ninety-nine per cent, 72% and 78% of the eggs were in the blastocyst stage in intact controls, ovariectomized and hypophysectomized rats. The remainder of the eggs were either morulae or degenerated. Blastocysts and morulae recovered from the hypophysectomized rats were transferred to the uteri of pseudopregnant recipients: 52–57% developed into normal term foetuses compared to 57% for intact controls. In hypophysectomized rats killed in the morning of day 6, the number of eggs recovered was greatly reduced as compared with rats killed on day 5. This loss of eggs was prevented by placing a ligature at the cervical end of the uterus in the morning of day 5. It was therefore concluded that the eggs had been expelled from the uterus into the vagina between days 5 and 6.