Absolute quantification and modulation of cytochrome P450 3A isoforms in cattle liver

In humans and laboratory animals, knowledge about cytochrome P450 (CYP) regulation and function is detailed and very extensive. However, CYPs have still been incompletely characterized in veterinary species so far. In this study, mRNA levels of three CYP3A enzymes (CYP3A28, CYPA38 and CYPA48) were measured in cattle liver by using quantitative real-time RT-PCR (qPCR) assays and an absolute quantification approach. In particular, the possible presence of breed-differences in CYP3A expression was investigated in five different meat cattle breeds (Charolais, CH; Piedmontese, PM; Blonde d’Aquitaine, BA; Marchigiana, MA; Valdostana, VALD) and the potential transcriptional effect of the prototypical inducer phenobarbital (PB) upon the CYP3A isoforms was evaluated. Cytochrome P450 3A38 showed the highest amounts of gene copy numbers, followed by CYP3A48 and CYP3A28. Significant breed-differences in CYP3A gene abundances were found, and PB significantly up-regulated all the CYP3As isoforms. The data provide new information about CYP3A expression in cattle, particularly the heterogeneity in the pattern of expression of distinct hepatic CYP3As (CYP3A38>3A48>>3A28), the significant effect of breed, and their common up-regulation following the exposure to PB, although with different orders of magnitude.