RADIOIMMUNOASSAY OF PLASMA NEUROPEPTIDE-Y USING WPLC FOR SEPARATION OF RELATED PEPTIDES AND FRAGMENTS

The aim of the present study was to characterize the basal level of pl asma neuropeptide Y (NPY) in man using HPLC for separation of related peptides and fragments and furthermore to determine to what extent pla sma NPY and/or PYY increased in response to food intake and exercise. Peptides and fragments were separated on a Pharmacia LKB Superdex(TM) 75 HR 10/30 column and measured by radioimmunoassay. Two commercially available antibodies were used. One antibody did not crossreact with p lasma PYY, whereas the other antibody detected both NPY and PYY, altho ugh with slightly different reactivities. Normal subjects were examine d in the basal state, after food intake and at the end of a 20 min per iod of heavy exercise. HPLC data indicated that basal values of plasma NPY were low and not greater than 2.5 pmoll(-1). During food intake t here was a marked increase in plasma PYY, whereas plasma NPY did not c hange. Expectedly, we observed an increase in plasma NPY at the end of a period of heavy exercise, whereas plasma PYY remained unchanged. It is concluded that the basal level of plasma NPY is considerably lower than reported in most studies in the literature. HPLC or similar meth ods should be used to characterize NPY-like immunoreactivities in furt her studies of plasma NPY during physiological and pathophysiological conditions.