Differential induction of cytochrome P450 1A1 and 1B1 mRNA in primary cultured bovine hepatocytes treated with TCDD,PBDD/Fs and feed ingredients

This study investigates the dose-dependent expression of CYP1A1 and CYP1B1 in primary cultured bovine hepatocytes exposed to TCDD, several polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) congeners and fish oil used as animal feed ingredients to identify their dioxin-like potentials. Hepatocytes were isolated from calf liver, cultured and treated for 24 h with the target compounds or extracts. Quantitative real time polymerase chain reaction analysis (qRT-PCR) showed that relative mRNA levels for CYP1A1 and CYP1B1 exhibited a dose-dependent induction by TCDD. The EC₅₀ of the TCDD concentration for CYP1A1 expression was approximately 4-fold less than that of CYP1B1. The estimated dioxin-like toxic potential of PBDD/Fs could be ranked in the following order: 2,3,7,8-TBDD > 1,2,3,7,8-PBDF > 2,3,4,7,8-PBDF > 1,2,3,6,7,8-HBDD. A good correlation was also observed in HRGC/HRMS-derived TEQs in fish oil samples and relative CYP1A1 mRNA induction in bovine hepatocytes treated with purified fish oil extracts. The data suggested that quantification of biomarker regulations in primary cultured hepatocytes could represent an effective tool for both the screening and study of various chemical entities in larger animals.