CIRCULATING NEUROPEPTIDE-Y IN PLASMA FROM UREMIC PATIENTS CONSISTS OFMULTIPLE PEPTIDE-FRAGMENTS

Increased plasma levels of neuropeptide Y (NPY)-like immunoreactivity (p-NPY-LI) have been described in hemodialysis (HD) patients. In this investigation the effect of a standard HD on p-NPY-LI, analyzed by rad ioimmunoassay and reverse-phase high performance liquid chromatography (HPLC), was studied. During dialysis p-NPY-LI increased from 128 +/- 5 to 154 +/- 8 pmol/l (p < 0.01). The change in p-NPY-LI during the tr eatment correlated with the ultrafiltration volume (r(s) = +0.72, p < 0.05). The HPLC separation revealed a complex pattern of NPY-immunorea ctive peptides. This was true of the plasma of the control subjects as well as of the uremic plasma. In the case of the controls and the HD patients prior to dialysis, the amount of NPY-LI was rather small. Aft er the dialysis qualitative as well as quantitative changes of the chr omatogram were found. Some of the peaks seemed to have a retention tim e similar to that of the known fragments of synthetic human NPY used a s markers. In conclusion, an increase in p-NPY-LI occurred during the dialysis, probably due to fluid removal. The increased level of NPY-LI in uremic plasma represents a mixture of different NPY fragments.