INHIBITION OF 3,3',4,4',5-PENTACHLOROBIPHENYL-INDUCED CHICKEN EMBRYOTOXICITY BY 2,2',4,4',5,5'-HEXACHLOROBIPHENYL

3,3',4,4',5-Pentachlorobiphenyl (pentaCB) caused a dose-dependent indu ction of chicken embryolethality, malformations, edema, and liver lesi ons at doses ranging from 0.5 to 12.0 mu g/kg. In contrast, no embryot oxicity was observed after treatment with 10, 25, or 50 mg/kg 2,2',4,4 ',5,5'-hexaCB. In eggs cotreated with 2.0 mu g/kg, 3,3',4,4',5-pentaCB plus 10, 25, or 50 mg/kg 2,2',4,4',5,5'-hexaCB, there was significant protection from 3,3',4,4',5-pentaCB-induced embryo malformations, ede ma, and liver lesions, whereas no inhibition of embryolethality was ob served. These results further extend the response-specific nonadditive interactions of binary mixtures of polychlorinated biphenyls (PCBs) a nd should be considered in the development of approaches for hazard as sessment of PCB mixtures and related compounds. (C) 1997 Society of To xicology.