Investigation of effects of pregnant mare serum gonadotropin (PMSG) on the chromosomal complement of CD-1 mouse embryos

Purpose: The objective of this study was to examine the effect of superovulatory doses of gonadotropins on the frequency of chromosomal abnormalities of mouse embryos. Methods: Chromosome analysis of 8- to 16-cell stage mouse embryos and zygotes was performed by a cytogenetic method. Results: There was no significant effect of the pregnant mare serum gonadotropin (PMSG) dose on the level of aneuploidy and structural abnormalities from 8- to 16-cell-stage embryos among superovulated groups. However, a simple dose-response relationship between the PMSG dose and the incidence of polyploidy was observed, with the level of polyploidy rising from 2.9% with 10 IU PMSG to 10.5% with 15 IU PMSG. In zygote stage, the proportion of polyploid embryos also increased as the dose increased, from 1.9% in 5 IU to 6.7% in 15 IU PMSG. It was observed that the extra chromosomal set in polyploidy embryos originated by both fertilization of a diploid oocyte and dispermy. Conclusions: These results indicate a dose-response relationship between the PMSG dose and the incidence of polyploidy in the CD-1 mouse. Both a disturbance at maturation division and an error at fertilization were the cause of polyploidy.