Dean Destructo
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The functions of melatonin in preovulatory fluid remain elusive. In the current study, we observed that the extremely high level of expression of MT1 in mice granulosa cells was rapidly induced byhCG (equivalent LH) within 2 hours and this was referred as MT1 surge. In cumulus cells, serotonin N-acetyltransferase (SNAT) was also up-regulated by hCG and led to elevated melatonin levels in ovarian follicle fluid. Melatonin application before MT1 surge significantly promoted embryo implantation and this was probably attributed to a rise in progesterone levels in the serum. The mechanistic studies indicated that melatonin/MT1 (MLT/MT1) signaling remarkably improved the expression of corpus luteum marker genes, i.e., Akr1c18, Cyp11a1. High-throughput sequencing results suggested that extracellular matrix (ECM) receptor interaction, focal adhesion and activation of PI3K/Akt pathway which are involved in granulosa cell luteinization might mediate the actions of MLT/MT1 signal. In addition, this effect on luteinization was compared in different species. It was verified that high melatonin levels exist in serum at oestrum of cows and helps to improve the first oestrus fecundation rate. These results suggested that both melatonin and MT1 are involved in the downstream reaction of hCG (LH) and they play important roles in luteinization. These findings provide the novel information on the physiology of melatonin in animal reproduction. This article is protected by copyright. All rights reserved.
