TOXICOKINETIC MIXTURE INTERACTIONS BETWEEN 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN AND 2,2',4,4',5,5'-HEXACHLOROBIPHENYL IN THE LIVER OF NEONATAL RATS AFTER PRENATAL AND POSTNATAL EXPOSURE

Pregnant rats received single oral doses of either 1.39 mug 2,3,7,8-te trachlorodibenzo-p-dioxin (TCDD)/kg, 164 mg 2,2',4,4',5,5'-hexachlorob iphenyl (HxCB)/kg, or a mixture of both compounds at day 16 of gestati on. The hepatic deposition of the compounds as well as CYP1A dependent 7-ethoxyresorufin-O-deethylation (EROD) and CYP2B dependent 7-pentoxy resorufin-O-depentylation (PROD) activity were studied in the mothers and offspring at day 10 after delivery. The HxCB deposition in the liv ers of mothers and offspring was approximately doubled when this compo und was coadministered with TCDD but HxCB coadministration did not inf luence hepatic TCDD deposition. It is concluded that the mechanisms be hind the toxicokinetic interactions between PCDDs and di-orthosubstitu ted PCBs in the liver are probably different for both groups of compou nds.