Prolonged Pregnancy in Albino Rat following Injection of Pregnancy Urine Extract

Abstract

Conclusion

Prolongation of pregnancy with development of fetuses of excessive size was regularly observed in rats following a single injection of 75 rat units of urine extract administered 4 days before term.

Previous observers have found marked alterations in the termination of pregnancy in the rat, following (1) injections of extracts of the corpus luteum (Nelson, et al. 1 ), (2) injections of extracts of the anterior pituitary (Teel, 2 Hain 3 ), and implants of the anterior pituitary (Hain^s), (3) injections of the urine of pregnant women (Levin, et al. 4 Hain 3 ), and (4) hypophysectomy (Pencharz and Long 5 ). The results of these investigations are difficult to evaluate in view of the differences in the substances administered, in their preparation and dosage, and in the parity and stage of pregnancy of the animals when treated.

In the present experiments the attempt was made to observe the duration of pregnancy in rats injected near term with a uniform dose of urine extract. The investigation was planned to take into account the factors which were found to be involved in prolongation of pregnancy in the rabbit (Snyder 6 ). A satisfactory method for the prolongation of pregnancy was found to be the subcutaneous injection of 75 R.U. of pregnancy urine (Antuitrin-S of Parke, Davis Co.) 19 days after mating. The day of recovery of spermatozoa from the vagina was designated day 1. The appearance of the placental sign, usually on the 14th day, also aided in estimating the duration of pregnancy.

In a consecutive series of 19 animals, prolongation of pregnancy occurred in 16. Usually hysterotomy was performed a few days past term. Hemorrhage or discharge from the vagina appeared in 12 cases. In one rat, laparotomy about the 40th day showed the uterus strikingly distended by fetuses so that it had the form of 3 large lumps. It was surrounded by dense adhesions to the abdominal organs.