Effects of polychlorinated biphenyls (PCBs) on in vitro fertilization in the mouse

Polychlorinated biphenyls (PCBs) are industrial chemicals that are long-lasting global environmental contaminants. PCBs have been reported to adversely affect reproduction in laboratory and wild animals by reducing the incidence of breeding and the survival rate of young. The present study was undertaken to determine the toxic potential of PCBs on in vitro fertilization (IVF) in the mouse. Aroclor 1221, 1254, and 1268, and 3, 3', 4, 4'-tetrachlorobiphenyl (TCB), a PCB congener, were added to IVF medium at various concentrations (0.01, 0.1, 1, and 10 micrograms/mL). Cumulus masses containing oocytes were obtained from superovulated B6D2F1 mice and cultured in medium containing PCB to which capacitated sperm were added. Oocytes were assessed for fertilization 20 to 24 h after insemination. A-1221, A-1268, and TCB reduced the fertilization rate at the 1 microgram/mL and 10 micrograms/mL doses, while inhibition of fertilization by A-1254 reached significance at 0.1 microgram/ml. Furthermore, all of these chemicals caused an increased incidence of degenerative ova and abnormal 2-cell embryos at the higher dose levels (1 microgram/mL and 10 micrograms/mL). The results suggest that higher dosages of PCB and TCB adversely affect fertilization and cause an increased incidence of degeneration of oocytes and abnormality in the early mouse embryos.