Abstract：
Goat bucks are seasonal breeders that show variation in sperm quality, endogenous melatonin (MLT), and presumably in the expression of MLT receptors on the sperm throughout the year, which may modify sperm freezability. The aim of this study was to determine whether sperm freezability is associated with (i) endogenous melatonin levels in seminal plasma and (ii) the expression of sperm plasma membrane melatonin receptors (MT1, MT2). To evaluate this, spermatozoa from seven Saanen goat bucks were cryopreserved throughout the year in Mexico using a standard freezing protocol. Seminal plasma MLT concentrations were determined by ELISA and the expression and localization of MT1 and MT2 were detected by immunocytochemistry and confirmed by western blotting. The recovery rate of progressive motility after thawing was higher in spring than autumn and winter; in contrast, the F pattern (CTC assay) was higher in winter than in the other seasons. A proportional increase in the AR pattern (CTC assay) was smaller in winter than in the other seasons and the proportion of sperm showing high plasma membrane fluidity was higher in spring than in summer and autumn. The seminal plasma MLT concentrations showed no significant interseasonal differences. The MT1 receptor was immunolocalised at the apical region of the sperm head, while MT2 was mainly localised in the neck. The relative expression of MLT receptors showed significant differences between summer and winter for all bands, except at 75 kDa of MT2. In conclusion, there was an association between the relative expression of MT1 and MT2 receptors throughout the year and sperm freezability in goat bucks in México. Post-thaw sperm quality is enhanced in semen samples collected during breeding season.
摘要：
山羊雄鹿是季节性繁殖者，它们显示出精子质量的差异，内源性褪黑素（MLT），大概是在精子上MLT受体全年的表达中，这可能会改变精子的冷冻能力。这项研究的目的是确定精子冷冻能力是否与（i）精浆中内源性褪黑激素水平和（ii）精子质膜褪黑激素受体（MT1，MT2）的表达有关。为了评估这一点，使用标准冷冻方案，在墨西哥全年冷冻保存了7只Saanen山羊的精子。通过ELISA测定精浆MLT浓度，通过免疫细胞化学检测MT1和MT2的表达和定位，并通过蛋白质印迹证实。春季解冻后渐进运动恢复率高于秋季和冬季；相比之下，冬季的F模式（CTC测定）高于其他季节。冬季AR模式（CTC测定）的成比例增加比其他季节小，春季表现出高质膜流动性的精子比例高于夏季和秋季。精浆MLT浓度无明显季节间差异。MT1受体免疫定位在精子头部的顶端区域，而MT2主要位于颈部。MLT受体的相对表达在夏季和冬季之间显示出所有条带的显着差异，除了在MT2的75kDa。总之,在墨西哥，一年四季MT1和MT2受体的相对表达与山羊雄鹿的精子冷冻能力之间存在关联。在繁殖季节收集的精液样品中，解冻后的精子质量得到了提高。
