COMPARATIVE ANALYSES OF THE NEUROPEPTIDE-F (NPF)-RELATED AND FMRFAMIDE-RELATED PEPTIDE (FARP)-IMMUNOREACTIVITIES IN FASCIOLA-HEPATICA AND SCHISTOSOMA SPP

Immunochemical techniques were used to determine the distribution, che mical characteristics and relative abundance of immunoreactivity (IR) to two native platyhelminth neuropeptides, neuropeptide F (NPF) (Monie zia expansa) and the FMRFamide-related peptide (FaRP), GNFFRFamide, in the trematodes, Fasciola hepatica and Schistosoma mansoni; the larger S. margrebowiei was used in the chemical analysis. Extensive immunost aining for the two peptides was demonstrated throughout the nervous sy stems of both F. hepatica and S. mansoni, with strong IR also in the i nnervation of muscular structures, including those associated with the egg-forming apparatus. The patterns of immunostaining were similar to those previously described for the vertebrate neuropeptide Y superfam ily of peptides and for FMRFamide. Ultrastructurally, gold labelling o f NPF- and GNFFRFamide-IRs was localized exclusively to the contents o f secretory vesicles in the axons and somatic cytoplasm of neurones. D ouble-labelling experiments showed an apparent homogeneity of antigeni c sites, in all probability due to the demonstrated cross-reactivity o f the FaRP antiserum with NPF. Radioimmunoassay of acid-ethanol extrac ts of the worms detected 8.3 pmol/g and 4.7 pmol/g equivalents of NPF- and FMRFamide-IRs, respectively, for F. hepatica, and corresponding v alues of 4.9 pmol/g and 4.3 pmol/g equivalents for S. margrebowiei. Ge l-permeation chromatography resolved IR to both peptides in discrete p eaks and these eluted in similar positions to synthetic NPF (M. expans a) and GNFFRFamide, respectively.