Abstract
During pregnancy, fetal lambs are exposed to low oxygen tension. Thus, an effective antioxidant mechanism is partially developed which sensitizes fetus to oxidative stress. Consequently, term and preterm neonates are susceptible to molecular and cellular injury caused by oxygen species (ROS). This study aimed to evaluate the development of antioxidant enzymes and oxidative profile of preterm (135 days of pregnancy) and term (145 days of pregnancy) neonatal lambs, correlating with clinical analysis. Preterm lambs had significantly (P ≤ 0.05) lower score of vitality (4.00 ± 1.10), bradycardia (99 ± 34 bpm) and bradypnea (13 ± 10 mpm). However, both groups were normothermic and euglycemic. Preterm group had low blood pH (7.07 ± 0.10) and both groups had hypercapnia, more severe in preterm group (85.52 ± 18.65 mmHg). In addition, premature newborns had lower pO2 (10.67 ± 5.65 mmHg) and SO2 (6.17 ± 5.85%) values. No significant difference (P ≥ 0.05) on antioxidant enzymes and oxidative stress were verified among experimental groups, although glutathione peroxidase negatively correlated with Apgar score, heart rate, SO2 and pO2. Our data show that preterm neonates are less adapted to the odds of labor and to overcome the immediate changes of extra-uterine life. Furthermore, we verified an influence of glutathione peroxidase in controlling oxidative stress, which highlights mature enzymatic mechanisms of cell redox, even in premature lambs.
Highlights
The neonatal period represents an adaptive phase in which clinical outcome is inwardly related to physiological maturity
The Apgar score as an indicator of vitality in the immediate neonatal period may vary among domestic species (Vannucchi et al, 2015b)
Lambs born at term in eutocia have Apgar score of approximately 6 immediately at birth (Vannucchi et al, 2012)
Summary
The neonatal period represents an adaptive phase in which clinical outcome is inwardly related to physiological maturity. Neonatal mortality rate during the first weeks in lambs is estimated to be higher than to 15% (Dwyer and Morgan, 2006). In premature lambs, such percentage can be much higher, resulting in significant economic losses to the sheep industry. Fetal lambs are exposed to low oxygen tension (O2; Gitto et al, 2002). The system of combating free radicals is partially developed and the imbalance between pro- and anti-oxidant systems sensitizes fetus to oxidative stress. With the onset of aerobic metabolism after birth, there is a significant increase in O2 consumption, which triggers the production of free radicals in the mitochondrial respiratory chain (Vlessis and Mela-Riker, 1989).
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