Melatonin regulates male reproductive function in seasonal and non-seasonal breeder mammals. The presence of melatonin membrane receptors (MT1 and MT2) in the testis and epididymis has been demonstrated in several species. Wild roe deer are a short-day breeding species characterised by a short rutting season lasting from mid-July to mid-August. The aim of this study was to determine the concentration of melatonin in the peripheral blood and the presence of MT1 and MT2 receptors in the testis and epididymis in male roe deer during the pre-rut (May), rut (July/August) and post-rut (September) periods. The melatonin concentration was higher in May (522.50 ± 54.20 pg/mL) compared to July/August (258.50 ± 36.82 pg/mL; P < 0.05). During September, the melatonin concentration was higher (393.50 ± 36.77 pg/mL) than in July/August (P < 0.05) but lower than in May (P < 0.05). Immunohistochemical analysis showed the presence of MT1 and MT2 receptors in Leydig cells, Sertoli cells and germ cells in the testis, in addition to the epithelial cells of the epididymis caput, corpus and cauda. MT1 and MT2 receptor expression in the testis and epididymis, assessed by Western blot, was higher in May and July/August (when spermatogenic and steroidogenic activity restarts and reaches its peak, respectively) compared to September (when spermatogenic and steroidogenic activity decreases). This could indicate a stimulatory effect of melatonin on testicular (i.e., steroidogenesis and spermatogenesis) and epididymal (i.e., spermatozoa maturation) function in male roe deer through the MT1 and MT2 receptors. Our results form the basis for further studies into the detailed mechanism of action of melatonin through MT1 and MT2 receptors for optimal reproductive activity in male roe deer and other mammals.

中文翻译：

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雄性狍精子发生过程中外周血褪黑激素浓度和雄性狍睾丸和附睾中褪黑激素受体（MT1和MT2）的浓度

褪黑激素调节季节性和非季节性繁殖哺乳动物的雄性生殖功能。睾丸和附睾中褪黑激素膜受体（MT1 和 MT2）的存在已在几个物种中得到证实。野生狍是一种短日照繁殖品种，其发情季节从七月中旬持续到八月中旬。本研究的目的是确定外周血中褪黑激素的浓度以及雄性狍在发情前（5 月）、发情期（七月/八月）和发情后的睾丸和附睾中 MT1 和 MT2 受体的存在情况。 -rut（九月）时期。与 7 月/8 月 (258.50 ± 36.82 pg/mL; P < 0.05) 相比，5 月的褪黑激素浓度较高 (522.50 ± 54.20 pg/mL)。9 月期间，褪黑激素浓度 (393.50 ± 36.77 pg/mL) 高于 7/8 月 (P < 0. 05）但低于 5 月份（P < 0.05）。免疫组织化学分析显示，除附睾头、体和尾的上皮细胞外，睾丸间质细胞、支持细胞和生殖细胞中还存在 MT1 和 MT2 受体。通过蛋白质印迹评估，睾丸和附睾中的 MT1 和 MT2 受体表达在 5 月和 7 月/8 月（当生精和类固醇生成活动分别重新开始并达到峰值）与 9 月（生精和类固醇生成活动降低时）相比更高。这可能表明褪黑激素通过 MT1 和 MT2 受体对雄性狍的睾丸（即类固醇生成和精子生成）和附睾（即精子成熟）功能有刺激作用。