Serum antioxidant enzymes activities and oxidative stress parameters as possible biomarkers of exposure in veal calves illegally treated with dexamethasone

Corticosteroids, particularly dexamethasone (DEX), are often illegally used in cattle to improve performances. This drug is usually administered per os, often in association with sexual steroids or β-agonists. Nowadays, relevant importance has been given to the use of biomarkers (BMs). Usually classified as BMs of exposure, response or toxic effect and susceptibility, they can be measured directly in target tissues or in surrogate ones, like urine or blood. It’s known that endogenous corticosteroids (i.e., cortisol) levels are likely to be modulated in cattle submitted to stressful conditions. Oestrogens and β-agonists may generate reactive oxygen species (ROS) and induce oxidative stress, respectively. Besides, the administration of an illicit drug cocktail consisting of oestrogen, β-agonist and DEX reduced the cattle serum antioxidant capacity and, in the meanwhile, increased the ROS amount. Therefore, the aim of the present study was the evaluation of a possible effect of DEX, illegally administered either intramuscularly or per os, on both the antioxidant status and oxidative stress in cattle. Ten cross-bred male veal calves were given DEX (2 mg pro capite injected twice, intramuscularly, at 8 days intervals; 0.4 μg pro capite, dissolved in milk and daily administered for 23 days). Five further animals were used as controls. Blood samples were withdrawn before (day 0, T0) and 4 (T1), 10 (T2), 14 (T3), 21 (T4), 28 (T5) days after the beginning of DEX oral administration. The oxidative stress (antioxidant capacity and ROS) and the antioxidant status (glutathione reductase, peroxidase and transferase, total sulphydryls content) were measured either by two colourimetric micro-methods or previously published procedures, respectively. Data obtained were statistically evaluated by repeated measures ANOVA and Tukey-Kramer multiple comparisons test (vs T0). Calves orally treated with DEX showed a significant increase of glutathione peroxidase isoenzyme activities (P<0.05) and also of the antioxidant capacity (P<0.05, P<0.01). No statistically significant differences were ever noticed for glutathione transferase, reductase or total sulphidryls content. Our results confirm that exogenous DEX may modulate the expression of glutathione peroxidase and, at least in part, of the antioxidant capacity. The former might be regarded as a possible biomarker of illegal oral low-dose administration of DEX in cattle. This study was supported by a grant from the Direzione di Sanità Pubblica, Assessorato alla Sanità, Regione Piemonte, Italy.