In vitro fertilization after in vivo treatment of rats with three reproductive toxicants.

One objective of these experiments was to establish a sensitive assay to evaluate fertilizing potential of rat gametes in vitro. A second objective was to evaluate this in vitro fertilization (IVF) assay as a method to detect in vivo effects of reproductive toxicants on male and female gametes using three known reproductive toxicants as model systems. The IVF assay with zona-free oocytes was more precise than the assay with cumulus-intact oocytes in these studies (coefficients of variation of 8.7 and 14.4%, respectively). Sperm fertilizing potential for zona-free oocytes was reduced by treatment of rats with m-dinitrobenzene (10-10 000 microg/kg) and ethylene glycol monomethyl ether (50-100 mg/kg) that had no effect on sperm motility. Molinate (60 mg/kg for 5 days) reduced sperm fertilizing potential concurrently with reductions in sperm motility. Neither molinate (60 mg/kg for 5 days) nor dinitrobenzene (0.002% in the drinking water for 14 days) administered to females seemed to affect the fertilizability of their oocytes. Ethylene glycol monomethyl ether treatment (0.15-0.25% in the drinking water for 14 days) reduced the number of ovulated oocytes. IVF is a means to evaluate toxicant effects on female gametes and demonstrates sperm's ability to interact with the oocyte plasma membrane.