INDUCTION OF SUPEROVULATION AND PREGNANCY IN MATURE MICE BY GONADOTROPHINS

Abstract

SUMMARY 1. The injection of 1 i.u. pregnant mares' serum (PMS) followed after 40 hr by 2 i.u. human chorionic gonadotrophin (HCG), or of 3 i.u. PMS followed by 3 i.u. HCG into mature female mice selected at random with regard to their oestrous cycle induces oestrus and mating in approximately 75%, and ovulation in 99% of them. 2. The induction of superovulation depends on the amount of PMS injected and on the strain of mice used. 3. Two types of egg are ovulated, one being normal and with a cumulus, the other degenerated and without cumulus. 93% of the normal eggs were fertilized and 98% of the pronucleate eggs possessed two pronuclei. 4. Approximately three-quarters of the females which mate in response to the injected gonadotrophins become pregnant, although this number was less than the number becoming pregnant after mating during natural oestrus. Many of the treated females carried their embryos to term and some gave birth to large litters, although resorptions, irregular distribution of embryos in the uterus, and difficulty during parturition occurred in some females. Mean litter size of the treated females was similar to that found after natural mating. 5. After more than one treatment with gonadotrophins, fewer females mated, ovulated, and became pregnant than after the first treatment. This reduction in response may have been due to the greater age of the females or to their decreased sensitivity to the hormones. 6. The value of the method as a technique for inducing oestrus, ovulation, and pregnancy in mature female mice is considered.