Reproductive Biology and Technology Research Team, National Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
Mol Reprod Dev. 2011 Apr;78(4):250-62. doi: 10.1002/mrd.21295. Epub 2011 Mar 4.
Melatonin is a multifunctional molecule that mediates several circadian and seasonal reproductive processes. The exact role of melatonin in modulating reproduction, however, is not fully understood-especially its effects on the ovarian follicles and oocytes. This study was conducted to investigate the expressions of the ASMT and melatonin-receptor MTNR1A and MTNR1B genes in bovine oocytes and their cumulus cells, as well as the effects of melatonin on oocyte nuclear and cytoplasmic maturation in vitro. Cumulus-oocyte complexes (COCs) from abattoir ovaries were cultured in TCM-199 supplemented with melatonin at concentrations of 0, 10, 50, and 100 ng/ml. The expression of ASMT, MTNR1A, and MTNR1B genes was evaluated by RT-PCR. Moreover, the effects of melatonin on cumulus cell expansion, nuclear maturation, mitochondrial characteristics and COCs steroidogenesis were investigated. Furthermore, the level of reactive oxygen species (ROS) was evaluated in denuded oocytes. Our study revealed that ASMT and MTNR1A genes were expressed in COCs, while the MTNR1B gene was expressed only in oocytes. Additionally, melatonin supplementation at 10 and 50 ng/ml to in vitro maturation medium significantly enhanced oocyte nuclear maturation, cumulus cell expansion and altered the mitochondrial distribution patterns, but had no effects on oocyte mitochondrial activity and COCs steroidogenesis. Melatonin-treated oocytes had a significantly lower level of ROS than controls. The presence of melatonin receptors in COCs and its promoting effects on oocyte nuclear and cytoplasmic events, indicate the potentially important roles of this hormone in regulating bovine oocyte maturation. Moreover, the presence of ASMT transcript in COCs suggests the possible involvement of these cells in melatonin biosynthesis.
褪黑素是一种多功能分子，介导几种昼夜节律和季节性生殖过程。然而，褪黑素调节生殖的确切作用尚不完全清楚-尤其是其对卵巢卵泡和卵母细胞的影响。本研究旨在研究牛卵母细胞及其卵丘细胞中 ASMT 和褪黑素受体 MTNR1A 和 MTNR1B 基因的表达，以及褪黑素对体外卵母细胞核和细胞质成熟的影响。从屠宰场卵巢中采集卵丘-卵母细胞复合物（COCs），并在含有褪黑素的 TCM-199 中培养，褪黑素浓度分别为 0、10、50 和 100ng/ml。通过 RT-PCR 评估 ASMT、MTNR1A 和 MTNR1B 基因的表达。此外，还研究了褪黑素对卵丘细胞扩展、核成熟、线粒体特征和 COCs 类固醇生成的影响。此外，还评估了去卵母细胞中的活性氧（ROS）水平。我们的研究表明，ASMT 和 MTNR1A 基因在 COCs 中表达，而 MTNR1B 基因仅在卵母细胞中表达。此外，在体外成熟培养基中添加 10 和 50ng/ml 的褪黑素可显著增强卵母细胞核成熟、卵丘细胞扩展并改变线粒体分布模式，但对卵母细胞线粒体活性和 COCs 类固醇生成没有影响。与对照组相比，褪黑素处理的卵母细胞中 ROS 的水平显著降低。COCs 中存在褪黑素受体及其对卵母细胞核和细胞质事件的促进作用，表明该激素在调节牛卵母细胞成熟中可能具有重要作用。此外，COCs 中存在 ASMT 转录本表明这些细胞可能参与褪黑素的生物合成。
