A new family member for gonadotropin-releasing hormone.

The two living representatives of the most ancient vertebrates, Agnathans, are lamprey and hagfish. Using immunological methods, we identified gonadotropin-releasing hormone (GnRH)-like molecules in the lamprey brain, but not hagfish. The lamprey GnRH was detected poorly by antisera directed at the C-terminus, suggesting that a C-terminal amino acid substitution may have occurred in the lamprey molecule compared with mammalian GnRH. In spite of this, lamprey and mammalian GnRH-like molecules have the same retention time on an isocratic HPLC system and parallel inhibition of mammalian 125I-GnRH in a radioimmunoassay. The lamprey GnRH-like molecule has a distinct HPLC elution pattern compared with dogfish shark, salmon, trout and probably birds. Thus lamprey GnRH represents another member of the growing family of GnRH molecules. Additionally, lamprey GnRH may be a stem molecule in the vertebrate evolution of GnRH.