title: Hepatic tyrosine aminotransferase and glucocorticoid abuse in meat cattle.
abstract: Besides being extensively applied as therapeutical remedies, glucocorticoids (GCs) - most notably dexamethasone or prednisolone - are also illegally used in livestock for growth-promoting purposes. This study was designed to assess the suitability of liver tyrosine aminotransferase (TAT), a gluconeogenic enzyme known to be induced by GCs, to act as a reliable candidate biomarker to screen for GC abuse in cattle. Enzyme activity was measured spectrophotometrically in liver cytosols or in cell extracts, and TAT gene expression was determined by real-time PCR. Compared with untreated veal calves, a notable scatter (20-fold) and much higher median values (3-fold) characterized TAT specific activity in liver samples from commercially farmed veal calves. A time-related increase in both enzyme activity and gene expression was detected in rat hepatoma cell lines treated with dexamethasone concentrations (10(-8) or 10(-9) m) in the range of those recorded in noncompliant samples from EU official controls. In experimental studies in which finishing bulls were administered GCs at growth-promoting dosages, however, no such changes were recorded in dexamethasone-treated animals; a statistically significant rise in liver TAT activity (+95%) only occurred in prednisolone-treated bulls. Although further research is needed to characterize the GC-mediated response in cattle liver, TAT does not appear to be a specific and sensitive biomarker of GC abuse in the bovine species.
authors.affiliation: Dipartimento di Patologia Animale, Università degli Studi di Torino, Grugliasco, Italia.
authors.forename: D
authors.initials: D
authors.lastname: Bertarelli
authors.forename: A
authors.initials: A
authors.lastname: Balbo
authors.forename: M
authors.initials: M
authors.lastname: Carletti
authors.forename: T
authors.initials: T
authors.lastname: Cannizzo
authors.forename: F
authors.initials: F
authors.lastname: Girolami
authors.forename: C
authors.initials: C
authors.lastname: Nebbia
mesh_terms: D000818:Animals; D015415:Biomarkers; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D002417:Cattle / Q000378:metabolism*; D045744:Cell Line, Tumor; D003907:Dexamethasone; D015971:Gene Expression Regulation, Enzymologic; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008113:Liver Neoplasms / Q000378:metabolism; D008297:Male; D012313:RNA / Q000235:genetics / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D015813:Substance Abuse Detection / Q000379:methods / Q000662:veterinary*; D014444:Tyrosine Transaminase / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D005938:Glucocorticoids; D012313:RNA; D003907:Dexamethasone; D014444:Tyrosine Transaminase