Viability of alpha-momorcharin-treated mouse blastocysts in the pseudopregnant uterus.

Mouse morulae and early blastocysts developed normally to the late blastocyst stage in the presence of alpha-momorcharin in culture. When these embryos were transferred to a pseudopregnant uterus, they showed a poor ability to induce the decidual reaction and many failed to implant. Those that had implanted showed retarded embryonic development and many implantation sites contained only trophoblastic giant cells and extraembryonic membranes. Implantation of blastocysts was inhibited when the recipient animal was given alpha-momorcharin at the time of embryo transfer. We suggest that termination of early pregnancy by alpha-momorcharin is the result of the deleterious effect of the protein on the implanting embryos and the endometrium.