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Hepatic tyrosine aminotransferase and glucocorticoid abuse in meat cattle

Authors


Prof. Carlo Nebbia, Dipartimento di Patologia Animale, Sezione Farmacologia e Tossicologia, Università degli Studi di Torino, Via Leonardo da Vinci 44, 10095 Grugliasco, Italia. E-mail:carlo.nebbia@unito.it

Abstract

Bertarelli, D., Balbo, A., Carletti, M., Cannizzo, T., Girolami, F., Nebbia, C. Hepatic tyrosine aminotransferase and glucocorticoid abuse in meat cattle. J. vet. Pharmacol. Therap. 35, 596–603.

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.

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