Transplantation of preimplantation hamster embryos.

Abstract

Since Heape (1890) first succeeded in transplanting rabbit embryos (four-cell stage), the transplantation of fertilized eggs and preimplantation embryos of laboratory animals has been progressively more successful (for review and bibliography, see Chang & Pickworth, 1969; Adams & Abbott, 1971), though few studies seem to have been made on the transplantation of hamster embryos. Blaha (1964) reported that 49\m=.\2%of six- to eight-cell embryos from young (2\m=1/2\-to 6-month-old) donor hamsters could develop into term fetuses when transplanted into young recipients, but that only 8\m=.\3%of embryos of the same developmental stage developed into fetuses when transplanted into old (14- to 10-month-old) recipients. The incidence of successful fetal development was also very low (4\m=.\5%) when the embryos from old donors were transplanted into young recipients. Orsini & Psychoyos (1965) transplanted hamster blastocysts into progesterone-treated females which had been previously ovariectomized, and found that some of the embryos could develop into live fetuses (7 to 12 days). According to Yang (cited from Chang & Pickworth, 1969), 49 to 54% of 3- to 4-day preimplantation hamster embryos could develop into fetuses following transplantation, when the reproductive phases of the donor and recipient females were synchronized. Asynchronous transplantation (Day-3 embryos to Day-4 uteri or Day-4 embryos to Day-3 uteri) resulted in a lower rate (14 to 35%) of successful fetal development. This communication reports the results of synchronous transplantation of preimplantation hamster embryos, including transplantation of one- and two-cell embryos. Female golden hamsters were raised in an air-conditioned room with a 12-hr light cycle (light, from 06.00 hours until 18.00 hours) and used in experiments when they weighed 90 to 120 g (2 to 3 months after birth). The oestrous cycle of each female was determined according to Orsini (1961), except that the day on which postoestrous vaginal discharge occurred was taken as the 1st day of the oestrous cycle. Between 21.00 hours and 22.00 hours on the 4th day of the cycle (when the animals were in heat), prospective recipient females were given mechanical vaginal/cervical stimulation in order to induce pseudopregnancy (Diamond & Yanagimachi, 1968). Females to be used as donors were mated with fertile males in the evening of the same day. The day following mating or vaginal stimulation was designated Day 1 of pregnancy or pseudopregnancy.