Cytochrome P450 inhibition profile in liver of veal calves administered a combination of 17β-estradiol, clenbuterol, and dexamethasone for growth-promoting purposes

The effects of the administration of a combination of 17 beta-estradiol (10 mg i.m. for three times at 17 intervals), dexamethasone (4 mg/day for 6 days and 5 mg/day for further 6 days, dissolved in milk), clenbuterol (20 mu g/kg b.w./day, dissolved in milk, for the last 40 days before slaughtering) for promoting (GP) purposes on liver drug metabolising capacity were studied in crossbred Friesian calves. Compared to controls, liver preparations from GP-treated calves showed an overall reduction the extent of the ill vitro ability to metabolize testosterone and a number of substrates, most those associated with CYP 2C or CYP 3A, which also displayed a reduced expression on western By contrast the tested hydrolytic and conjugative pathways were not significantly affected. As by northern blot, the lack of significant differences in CYP mRNA abundance point to a post-transcriptional effect of the GP combination. The remarkable involvement of the affected hepatic CYPs in the transformation of both steroid hormones and a large array of commonly used drugs may result In further accumulation Of undesirable residues in meat and offals of illegally treated calves. (c) 2008 Elsevier Ltd. All rights