SUPERFECUNDITY IN RATS TREATED WITH MARE GONADOTROPIC HORMONE

Abstract

The effect of mare gonadotropic hormone on fecundity was detd. in 155 instances in mature animals and in 288 immature animals. Only in the immature animal did the injs. result in superovulation and in the implantation of a number of fetuses far exceeding that found in the normal mature [female]. Mature rats were injected with amts. ranging from 3 to 24 units in dioestrum, oestrus, and metoestrum. The average litter size and the % of large litters were increased by injecting 12 rat units in metoestrum; but no litter exceeded in size the largest found in control animals. Excessive doses reduced the % of fertile matings in both mature and immature rats. Implantation of fetuses occurred in rats injected on the 22d day and mated on the 25th day of age. Of rats injected on the 26th to 31st day of age 49% mated. Necropsy on the 10th to 12th day of pregnancy revealed an astonishing number of implanted fetuses[long dash]as many as 28. Of the rats sacrificed at this time, 38% had in excess of 20 fetuses. One rat sacrificed on the 17th day had 26 normal-appearing fetuses; and another on the 21st day had 23 living fetuses. In a rather small series the largest number born was 17 living young.