Oxidative state in equine neonates: Anti- and pro-oxidants.

Abstract

In newborns, exposure to the extrauterine environment with high oxygen tension and sudden pulmonary adaptation leads to an increase in reactive oxygen species (ROS). ROS have several physiological roles, which are essential for neonatal development, however, when unbalanced, these highly unstable molecules can cause cellular destabilisation, compromising vital processes. To characterise the oxidative status in healthy equine neonates, evaluating an indicator of lipid peroxidation and both enzymatic and nonenzymatic antioxidant systems, during the first week of life. Experimental cohort. Twenty-four foals were evaluated, with blood collections performed at 5minutes, 12, 72 and 168hours after birth. The degree of lipid peroxidation was quantified using Thiobarbituric Acid Reactive Substances (TBARS). Superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic activities, and total, conjugated and unconjugated serum bilirubin levels were also analysed. Comparisons were performed using ANOVA followed by a Tukey's test. Additionally, dependent variables were also evaluated with Pearson's correlation tests. Higher GPx activity was observed at 12 and 72hours when compared to 5minutes. An increase in TBARS levels was found at 5minutes after birth, followed by a decrease at 72hours and stabilisation through subsequent moments until 168hours after birth. No differences were observed in SOD activity when comparing the four time points. Bilirubin concentrations were lower at 5minutes after birth and total and unconjugated bilirubin increased at 12hours and decreased between 72 and 168hours after birth. Lipid peroxidation at birth was high, suggesting an increase in ROS levels relating to physiological events in neonatal adaptation. Antioxidant systems, involving unconjugated bilirubin and GPx, were activated and these biomolecules act concomitantly to reduce ROS levels, thus maintaining oxidative homeostasis. Overall, our results suggest a pro-oxidant balance during the first 168hours after birth in equine neonates.