CONCOMITANT DIETARY EXPOSURE TO POLYCHLORINATED BIPHENYLS AND POLYBROMINATED BIPHENYLS - TISSUE DISTRIBUTION AND ARYLHYDROCARBON HYDROXYLASE-ACTIVITY IN LACTATING RATS

Polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) stimulate microsomal mixed function monooxygenases in liver and extrahepatic tissues. These compounds accumulate to high concentration in fatty tissues and are excreted into milk. Human populations that have been exposed to PBBs are also likely to have been exposed to PCBs. Therefore, to assess potential hazard of simultaneous exposure to PCBs and PBBs, it was of interest to determine the distribution of PCBs (Aroclor 1254) and PBBs (Firemaster BP6) in several tissues of lactating rats, to determine the concentrations of both agents in milk and to study the effects of these agents on hepatic and extrahepatic arylhydrocarbon hydroxylase (AHH) after concomitant dietary exposure. Sprague-Dawley rats were placed on diets containing PBBs and/or PCBs from the eighth day of pregnancy to 14 days postpartum. Treatment with the highest dose of PBBs (200 ppm) retarded both dam and pup body weight gain. Stimulation of AHH was greater after treatment with PBBs alone than PCBs alone. Extrahepatic tissue concentrations of PCBs and PBBs were similar regardless of whether these agents were administered together or alone. Liver and milk contained lower concentrations of PBBs after treatment with an equal mixture of PCBs and PBBs than when PBBs were administered alone. Milk contained higher concentrations of PCBs than PBBs indicating that this route of excretion may be more important for PCBs. © 1979.