FMRFamide-related peptides from the kidney of the snail, Helisoma trivolvis.

Three FMRFamide-related peptides (FaRPs) were purified and characterized from the kidney of the snail, Helisoma trivolvis, by HPLC and detected using two radioimmunoassays (RIA) for FaRPs. Automated sequencing and mass spectrometry of the isolated peptides suggest the following sequences: Phe-Met-Arg-Phe-NH2 (FMRFamide), Phe-Leu-Arg-Phe-NH2 (FMRFamide), and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide). The FaRPs, predominantly the heptapeptides, were also detected by HPLC and RIA in other osmoregulatory tissues such as the skin, mantle, and the hemolymph. The level of FaRPs, detected by radioimmunoassay, appears to be lower in snails kept under hyposmotic stress than in snails kept under isosmotic stress. The FaRPs appear to be involved in osmoregulation in H. trivolvis.