Bioavailability and biotransformation of 3,4,3′,4′-tetrachlorobiphenyl (TCB) in in situ intestinal preparations of uninduced and TCB induced channel catfish

Diet is a major route of exposure of polychlorinated biphenyls for aquatic animals living in contaminated environments. This study investigated systemic bioavailability and intestinal metabolism of [14C]- 3,4,3′,4′-tetrachlorobiphenyl (TCB) in channel catfish, relative to TCB micelle solubility and TCB preexposure, using in vitro methods and in situ isolated intestinal preparations. Results showed that micelle fatty acid composition affected TCB solubilization in vitro, as well as systemic bioavailability of [14C]-TCB delivered in situ. Systemic bioavailability of [14C]-TCB was reduced by TCB dietary preexposure at two doses. TCB was scantily metabolized in the catfish intestine to 2-OH-TCB in the in situ preparation. High-dose TCB preexposure compositely induced aryl hydrocarbon hydroxylase (AHH) activity compared to other treatments, but had no significant effect upon intestinal cytochrome P450 content and glutathione-S-transferase (GST) activity. These results suggest that TCB partitioning and bioavailability may be influenced by dietary fatty acid composition and TCB preexposure. Furthermore, these results indicate that the intestine can minimally influence the metabolite profile of absorbed TCB.