The Influence of Age and Gender on the Serum XOR Activity, Leukocyte Gene Expression of XOR and MPO, and Biochemical Parameters in Newborn Foals.
Authors: Ghaeli Taranom, Karimi Behnaz, Kojouri Gholam Ali, Dehkordi Rouzbeh Razavi, Ahadi Ali Mohammad
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Xanthine oxidoreductase (XOR) and myeloperoxidase (MPO) are key oxidative enzymes in the foal's innate immune response during the critical early postnatal period, yet their developmental trajectory has received limited attention. Researchers tracked serum XOR activity, leukocyte gene expression of XOR and MPO, and related biochemical markers in 16 healthy Darehshuri foals at days 1, 7, 15, 30, and 60 of life, using real-time RT-PCR and standard serum analysis. XOR activity peaked at birth—likely due to physiologic hypoxia during parturition—then declined significantly with age and showed no sex-dependent variation, whilst MPO gene expression increased progressively and demonstrated sex-dependent differences, peaking at day 30 when neutrophil phagocytic capacity may be heightened. Serum creatinine, total protein, and albumin were elevated at birth before normalising, whereas uric acid remained low initially, with no correlation to XOR activity despite its theoretical role as substrate feedback inhibition. For practitioners managing neonatal foals, these findings suggest that the dramatic drop in XOR activity after birth is a normal developmental adaptation rather than pathological, whilst the age- and sex-related increase in MPO expression reflects maturation of the neutrophil-mediated immune response—important context when interpreting inflammatory markers and oxidative stress indicators in foals during their first two months of life.
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Practical Takeaways
- •XOR and MPO enzyme activity patterns in early life reflect normal neonatal immune maturation; clinicians should establish age-appropriate reference ranges for these markers in foals rather than using adult values
- •Sex-dependent differences in MPO expression suggest gender-specific immune development in foals, which may influence disease susceptibility and warrant consideration in clinical evaluation of sick neonates
- •The significant changes in these oxidative stress markers during the first 60 days of life provide potential biomarkers for assessing immune competence and health status in newborn foals
Key Findings
- •XOR activity was highest at birth due to physiologic hypoxia and decreased significantly over 60 days without sex differences
- •MPO gene expression increased with age and was sex-dependent, with highest levels at 30 days correlating with neutrophil phagocytic capacity
- •Positive correlation observed between XOR mRNA and serum XOR activity at 15 days of age
- •Creatinine, total protein, and albumin concentrations were elevated at birth while uric acid levels were lower, normalizing with age