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

Abstract

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 B 6C 3F 1 female mice and inseminated in vitro with spermatozoa from B 6C 3F 1 males. 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 μ m of Cd and a decrease in sperm motility was noted in the 1.6 μ m 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 μ m Cd developed to blastocysts at rates comparable to that of the controls. In the 1.6 μ m group, however, only one (3.2%) of the two-cell embryos developed to the blastocyst stage. Blastocysts from 0.4 μ m 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.