Primary hepatocytes as an useful bioassay to characterize metabolism and bioactivity of illicit steroids in cattle.

Cattle hepatocytes have already been used in veterinary in vitro toxicology, but their usefulness as a multi-parametric screening bioassay has never been investigated so far. In this study, cattle hepatocytes were incubated with illicit steroids/prohormones (boldenone, BOLD; its precursor boldione, ADD; dehydroepiandrosterone, DHEA; an association of ADD:BOLD), to characterize their transcriptional effects on drug metabolizing enzymes (DMEs) and related nuclear receptors (NRs), on cytochrome P450 3A (CYP3A) apoprotein and catalytic activity as well as to determine ADD and BOLD metabolite profiling. DHEA-exposed cells showed an up-regulation (higher than 2.5-fold changes) of three out of six NRs, CYP2B22 and CYP2C87; likewise, ADD:BOLD increased CYP4A11 mRNA levels. In contrast, a reduction of CYP1A1 and CYP2E1 mRNAs (lower than 2.5(-1)-fold changes) was noticed in ADD- and DHEA-incubated cells. No effect was noticed on CYP3A gene and protein expression, though an inhibition of 6β-, 2β- and 16β-hydroxylation of testosterone (higher than 60% of control cells) was observed in ADD- and BOLD-exposed cells. Finally, 17α-BOLD was the main metabolite extracted from hepatocyte media incubated with ADD and BOLD, but several mono-hydroxylated BOLD and ADD derivatives were detected, too. Collectively, cattle hepatocytes can represent a complementary screening bioassay, useful to characterize growth promoters metabolite profiling and their effects upon DMEs expression, regulation and function.