查看文章

In vertebrates, the gonadotropin-releasing hormone (GnRH) decapeptide is secreted from hypothalamic nerve terminals to regulate reproduction via control of synthesis and release of pituitary gonadotropins. Only one GnRH peptide has been found in mammals, with one exception, although numerous other vertebrate species express more than one of the eight known decapeptide forms as shown by immunocytochemical labeling of distinct cell groups in the brain. However, neither the functional nor the evolutionary relationships among these GnRH forms are clear, because only one preprohormone gene sequence from any species has been reported. The most ubiquitous alternative form of GnRH is [His5,Trp7,Tyr8]GnRH (also referred to as chicken-II), which differs from the mammalian sequence at amino acids 5, 7, and 8. This peptide has been shown to have the most potent releasing-hormone activity, although …