Role of biotransformation in the in vitro preimplantation embryotoxicity of naphthalene.

The in vitro developmental toxicity of the bicyclic aromatic hydrocarbon naphthalene was characterized with a preimplantation mouse embryo culture system. Day 3 ICR mouse blastocysts were co-cultured with naphthalene for 1 h either alone or in media supplemented with an Aroclor-induced rat S-9 preparation and cofactors. Toxin-treated blastocysts were subsequently cultured in NCTC 109 media with 10% fetal bovine serum for 72 h to observe the developmental effects of exposure. Developmental parameters observed included viability, hatching, culture dish attachment and trophoblastic outgrowth with the presence of a distinct inner cell mass. At media concentrations up to 0.78 mM, naphthalene alone exhibited negligible toxic effects in culture; however naphthalene co-cultured with Aroclor-induced rat hepatic S-9 fractions exhibited concentration-dependent embryolethality with an approximate LC50 of 0.18 mM in media. Naphthalene also induced concentration-dependent embryotoxicity at all observed parameters in S-9-supplemented media at concentrations ranging from 0.20 to 0.78 mM. These findings document the role of biotransformation in naphthalene's embryotoxicity to early mouse blastocysts and implicate naphthalene as a potentially embryotoxic and abortifacient component of polycyclic aromatic hydrocarbon mixtures.