Neuropeptide Y, peptide YY and C-terminal fragments release histamine from rat peritoneal mast cells.

1. Neuropeptide Y (NPY) and peptide YY (PYY) seem to act on at least two receptor subtypes, Y1 and Y2. The Y1-receptor requires the whole C-terminally amidated NPY/PYY molecule whereas the Y2-receptor in addition recognizes C-terminal fragments of the two peptides. The present study was designed to elucidate whether NPY and related peptides were able to release histamine from isolated peritoneal mast cells of the rat. 2. NPY, NPY 15-36, NPY 22-36, NPY 26-36 and desamido-NPY evoked a concentration-dependent release of mast-cell histamine. The pEC15 values for NPY 15-36 and NPY 22-36 were higher, while the pEC15 value for NPY 26-36 was lower than that for NPY. At the highest concentration tested (0.1 mM), NPY and its C-terminal fragments released between 30 and 40% of the total histamine content. At the same concentration desamido-NPY released about 20%. 3. PYY and PYY 15-36 also evoked a concentration-dependent release of mast-cell histamine. PYY was more effective than PYY 15-36 since, at 0.1 mM, PYY released about 33%, while PYY 15-36 released about 15% of the total histamine content. Pancreatic polypeptide (PP) and the Y1-receptor-selective agonist [Pro34]NPY were virtually inactive. 4. The effect profile of the NPY/PYY-related peptides suggests that they act on the mast cells by a mechanism that does not involve either of the receptor subtypes hitherto described. The kinetics of the NPY-evoked histamine release may suggest that positively charged amino acid residues of NPY/PYY release mast-cell histamine by a non-receptor mechanism, as has been suggested for substance P and other basic peptides.