Oxidative state in equine neonates: Anti‐ and pro‐oxidants

Abstract

Background 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. Objectives 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. Study design Experimental cohort. Methods Twenty‐four foals were evaluated, with blood collections performed at 5 minutes, 12, 72 and 168 hours 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. Results Higher GPx activity was observed at 12 and 72 hours when compared to 5 minutes. An increase in TBARS levels was found at 5 minutes after birth, followed by a decrease at 72 hours and stabilisation through subsequent moments until 168 hours after birth. No differences were observed in SOD activity when comparing the four time points. Bilirubin concentrations were lower at 5 minutes after birth and total and unconjugated bilirubin increased at 12 hours and decreased between 72 and 168 hours after birth. Conclusions 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 168 hours after birth in equine neonates.

Comparative Assessment of Oxidative and Antioxidant Parameters in Mule and Horse Neonates during Their First Month of Extrauterine Adaptation

“…This would corroborate the data observed in this study, where we had the highest concentrations of IB at 6, 12, and 24 h of life, and the SOD activity did not vary at these moments. Similar results were found in humans [23] and equine [7] neonates, where no variations were observed in the SOD enzymatic activity, while the indirect bilirubin was elevated.…”

“…However, at 30 days, there was a significant increase in GPx activity along with a lower concentration of TBARS. Previous studies in horses have demonstrated a significant decrease in TBARS concentrations from 5 min after birth to 72 and 168 h postpartum; this reduction indicates that they showed peripartum peroxidation [7]. In another study, horse neonates showed high levels of TBARS at birth, with a subsequent decrease up to 7 days, and lower GPx activity at birth with an increase at 12 h of life [6].…”

“…On the other hand, the non-enzymatic defense mechanism is composed of reducers of free radicals. Among low-molecular-weight biological non-enzymatic antioxidants, bilirubin stands out [6,7]. Currently, it is known that under physiological conditions, bilirubin has a potent antioxidant role [8] and is highly lipophilic, protecting against oxidative lipid degradation.…”

“…The antioxidant and oxidative states have been studied in different domestic animal species, with emphasis on the gestational, parturition, and neonatal periods in equine [7,9], bovine [8], ovine [10,11], and porcine [12] species. However, there are no published reports of oxidative and antioxidant profile in mule foals.…”

Maternal and Neonatal Evaluation of Derived Reactive Oxygen Metabolites and Biological Antioxidant Potential in Donkey Mares and Foals

“…The oxidative status has also been studied in horses [25][26][27][28][29][30][31][32][33], and there are also a few studies on donkeys [34][35][36]. In horses, studies assessing oxidative status in relation to exercise reported higher concentrations of derived reactive oxygen metabolites (d-ROMs) after sub-maximal exercise on a treadmill, compared to rest [26,27].…”