Bioavailability of PCBs to male laboratory rats maintained on litters of contaminated soils: PCB burden and induction of alkoxyresorufin O-dealkylase activities in liver and lung.

Male rats from the Sprague-Dawley laboratory strain were maintained in the laboratory during 3 days and 1 night on litters containing a reference soil and different amounts of a soil, mainly polluted by PCBs (207 ppm expressed in Aroclor(R) 1254; SIII soil). Two categories of biomarkers of exposure were measured in both liver and lung of these rats: PCB burdens and activities of microsomal liver and lung cytochrome P450-dependent mono-oxygenases, namely ethoxy-, pentoxy-, and benzoxy-resorufin O-dealkylase activities (EROD, PROD, and BROD, respectively). PCB burdens in liver and lung of rats exposed to SIII soil were 1,845 and 241 ppb, respectively (expressed in Aroclor(R) 1254 equivalents). EROD, PROD, and BROD were significantly induced in the liver of rats exposed to SIII soil, while only EROD activity was induced in the lung. Induction of hepatic EROD activity was approximately 3- to 5.4-fold; pulmonary EROD activity was induced by 9- to 12-fold. In the lung, PROD and BROD activities were inhibited. When rats were exposed to SIII soil diluted with various amounts of standard ISO soil, a nearly linear dose-response relationship was found between the level of PCBs in the litter and EROD activity in both liver and lung. A nonlinear dose-response relationship exists with hepatic BROD activity; no dose-response relationship was observed with hepatic PROD and pulmonary PROD and BROD activities. EROD activity measurement in both liver and lung of rats maintained on a litter of PCB polluted soil was used to assess the bioavailability to mammals of PCBs.