ISOLATION AND PRELIMINARY BIOLOGICAL CHARACTERIZATION OF KPNFIRFAMIDE, A NOVEL FMRFAMIDE-RELATED PEPTIDE FROM THE FREE-LIVING NEMATODE, PANAGRELLUS-REDIVIVUS

A novel FMRFamide-related heptapeptide, Lys-Pro-Asn-Phe-Ile-Arg-Phe-NH 2 (KPNFIRFamide), was isolated and characterized from acid ethanol ext racts of the free-living nematode, Panagrellus redivivus. Whole-worm e xtracts contained greater than or equal to 9 pmol KPNFIRFamide/g wet w eight. A synthetic replicate of this peptide induced a rapid relaxatio n of tone and inhibited spontaneous contractility in isolated innervat ed and denervated body-wall muscle strips of the parasitic nematode, A scaris suum. KPNFIRFamide (0.1 nM) induced measurable relaxations in 5 0% of the muscle preparations examined. Concentrations greater than or equal to 0.3 nM induced relaxation in 100% of muscle preparations exa mined. The relaxation was short-lived at concentrations of peptide gre ater than or equal to 1 mu M and displayed a profile typical of recept or desensitization. These data suggest the occurrence of a closely rel ated peptide in A. suum and add further evidence to the concept of pri mary structural conservation of FaRPs within the nematodes.