SUPEROVULATION AND SUPERPREGNANCY IN THE GOLDEN HAMSTER*

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Abstract
Pregnant mare serum gonadotropin (PMSG) treatment given in the morning or afternoon on any day of the 4 day estrous cycle and human chorionic gonadotropin (HCG) given 2 days later successfully induced superovulation in the golden hamster. The minimum interval between PMSG and HCG necessary to obtain consistent superovulation was approximately 44 h. The lowest ovulation rate was obtained following PMSG treatment on the afternoon of day 4 although this time coincides with the maximum endogenous FSH [follitropin] level, necessary for the maturation of the next crop of follicles destined to ovulate. Some 38-100% of superovulated females in 4 different treatment groups became superpregnant after natural mating. Some treated females exhibited 2 consecutive nights of estrus with ovulation apparently occurring during the 2nd night. Superpregnant females delivered super size litters, up to 27 live-born pups. The ultimate litter size appeared to be established after day 3 and prior to day 8 of superpregnancy. A 1 day extension of the normal 16-day gestation period was observed in 31% of superpregnancies. Unilateral pregnancies were observed at autopsy in 44% of treated females which received the high dose of PMSG (30 IU). The progeny of superovulated females reproduced normally at maturity. The results indicate that ova from superovulated female hamsters are capable of full normal development.