Retained developmental capacity of blastocysts transferred from lead-intoxicated mice

Blastocysts from mice injected with an implantation-inhibiting dose of lead were transferred nonsurgically to pregnant foster mothers. This was done to obtain information about the ability of these blastocysts to implant and to develop into late fetal stages. There was no difference in the ability of lead-treated blastocysts to implant as compared with the transferred nontreated blastocysts. Nor was there any effect of the exposure to lead before implantation upon the development of the blastocysts into normal fetuses. The results indicate that the preimplantation blastocysts are protected from possible harmful influences from the lead treatment of the mothers, and that the implantation failure in lead-treated mice is not due to the inability of the blastocysts to implant. A significant increase in the frequency of exencephaly was observed in fetuses derived from transplanted blastocysts as compared with those from normal pregnant mice.