摘要：

Abstract:  Melatonin influences insulin secretion both in vivo and in vitro. (i) The effects are MT1-and MT2-receptor-mediated. (ii) They are specific, high-affinity, pertussis-toxin-sensitive, Gi-protein-coupled, leading to inhibition of the cAMP-pathway and increase of insulin release. Furthermore, melatonin inhibits the cGMP-pathway, possibly mediated by MT2 receptors. In this way, melatonin likely inhibits insulin release. A third system, the IP3-pathway, is mediated by Gq-proteins, phospholipase C and IP3, which mobilize Ca2+ from intracellular stores, with a resultant increase in insulin. (iii) Insulin secretion in vivo, as well as from isolated islets, exhibits a circadian rhythm. This rhythm, which is apparently generated within the islets, is influenced by melatonin, which induces a phase shift in insulin secretion. (iv) Observation of the circadian expression of clock genes in the pan

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