In vitro exposure of male and female mice gametes to cadmium chloride during the fertilization process, and its effects on pregnancy outcome.

The effect of cadmium chloride (Cd) on gamete fusion in vitro was evaluated, with further observations of the embryonic development and assessment of the pregnancy outcome of the in vitro fertilized mice. Oocytes were recovered from superovulated B6C3F1 females. Of 1210 control oocytes, 53.2% cleaved into two-cell stage embryos. Of these, 46.6% developed into blastocyst stage embryos which were then surgically transferred to pseudopregnant female CD-1 mice. Of a total of 63 implanted embryos, 8 (12.7%) developed in utero to live fetuses. Teratological examinations of these "test-tube" mice revealed no signs of abnormalities caused by in vitro culture. Male and female gametes were exposed to 0.4, 0.8, or 1.6 microM of Cd and a decrease in sperm motility was noted in the 1.6 microM group. Nevertheless, even in the highest concentration used, 56.4% of the ova cleaved into the two-cell stage, thus indicating no effect of Cd on initial gamete interaction. Gametes that had been treated with 0.4 and 0.8 microM Cd developed to blastocysts at rates comparable to that of the controls. In the 1.6 microM group, however, only one (3.2%) of the two-cell embryos developed to the blastocyst stage. Blastocysts from 0.4 microM Cd-treated gametes were then transferred to surrogate dams. Statistically significant blastocyst losses were recorded during the implantation period, whereas the pregnancy rate and the numbers of resorbed and live fetuses, were comparable to those of the controls. The offspring exhibited no malformations, and their body weights remained within the control values.