NEUROPEPTIDE FF-LIKE IMMUNOREACTIVITY IN HUMAN PLASMA

In order to examine whether neuropeptide FF (NPFF), an octapeptide wit h pain-modulating and blood pressure-raising properties in the rat, is present in circulating human blood, a radioimmunoassay (RIA) was esta blished. Using this highly specific and sensitive RIA, the mean concen tration of NPFF in human plasma was 2.9 pg/ml +/- 1.1 (n = 111). The c oncentration did not correlate with age or sex. Reversed-phase high pr essure liquid chromatography (HPLC) followed by RIA using two differen t antisera for NPFF showed that plasma NPFF eluted in a position ident ical to that of synthetic NPFF. In view of published Kd values (0.06 m M) for NPFF receptor, the concentrations detected of NPFF in human pla sma may be too low for systemic actions. Thus, plasma NPFF may represe nt leakage of the peptide from nervous tissue.