Antioxidant components of ram seminal plasma are influenced by age, season, and the rsapolymorphism of the mtnr1agene

Abstract

Melatonin regulates reproductive seasonality in sheep, and its concentration in the blood plasma is influenced by day length and age. It can act directly or by modulating antioxidant defense enzymes. The RsaI polymorphism (g.17355458 C > T) of the melatonin receptor MT1 gene (MTNR1A) has been associated with changes in ram semen and reproductive behavior. But it remains unknown how age and this polymorphism affect melatonin concentration and the activities of antioxidant defense enzymes in ram seminal plasma. The aim of this study was therefore to analyze the effect of the RsaI polymorphism on melatonin levels and the activities of catalase (CAT), glutathione reductase (GRD), and glutathione peroxidase (GPx) in the seminal plasma of young and adult rams carrying different MTNR1A genotypes. For this purpose, seminal plasma was obtained from 15 young (16-month-old) and 9 adult (5-year-old) genotyped rams, and melatonin levels and CAT, GRD, and GPx activities were assessed for a year. Adult rams had higher melatonin concentrations in their seminal plasma than young rams. Adult CC and CT rams had the highest melatonin levels during the reproductive season, whereas young rams showed no differences between seasons. Adult rams also showed higher levels of GRD and GPx activity during the reproductive season; however, young rams showed higher levels of GPx activity during the non-reproductive season than during the reproductive season. These findings highlight the importance of considering the animal age when analyzing ram seminal plasma and its components.