Cross-reactivities of neuropeptide Y and peptide YY with pancreatic polypeptide antisera: evidence for the existence of pancreatic polypeptide in the brain.

Highly purified neuropeptide Y (NPY) and peptide YY (PYY) did not cross-react in our human pancreatic polypeptide (hPP) radioimmunoassay, nor did 125I-labelled NPY and PYY, even with anti-hPP serum at low dilution (1:1000). However, both [125I]NPY and [125I]PYY significantly cross-reacted with anti-bovine PP (bPP) serum at low dilution (1:1000, similar to that used in immunohistochemistry). These results suggest that radioassayable hPP-like peptide in the porcine or canine brain is probably pancreatic polypeptide itself, otherwise immunohistochemically detected bPP-like peptide may represent both NPY and PP.