Comparative immunohistochemical and biochemical analysis of pancreatic polypeptide-like peptides with special reference to presence of neuropeptide Y in central and peripheral neurons.

Antisera raised against porcine neuropeptide Y (NPY) and peptide YY (PYY) were characterized with regard to immunohistochemical staining, cross-reactivity to several pancreatic polypeptide (PP)-related peptides, and radioimmunoassayable tissue levels in the rat and pig. The NPY antiserum (102B) reacted with nerves in many areas of both the central and peripheral nervous systems, but it did not stain endocrine cells of the pancreas or intestine. No evidence for any cross-reactivity of the NPY antiserum with related peptides of the PP family, such as avian PP, bovine PP, PYY, gamma-MSH, FMRF-amide, or avian PP (31-36), was obtained. The NPY antiserum was N-terminally directed, and regional levels of NPY as seen by radioimmunoassay paralleled well the occurrence of NPY-immunoreactive structures seen in the immunohistochemical study. High pressure liquid chromatography analysis revealed that the NPY-immunoreactive material from cerebral cortex and vas deferens had elution profiles similar to those of standard porcine NPY. The PYY antiserum mainly stained endocrine cells in the pancreas and intestine as well as a small neuron system in the brainstem of the rat. Although this antiserum had a slight cross-reactivity to NPY in radioimmunoassay, the neuronal PYY staining was separate from that of NPY. High levels of PYY were found in the intestine, and levels above the threshold were also seen in the dorsal vagal complex of the rat. The other antisera investigated (raised against avian PP, bovine PP, gamma-MSH, and FMRF-amide) caused neuronal staining that was abolished by preabsorption with NPY. This was also seen even if no detectable cross-reactivity with NPY was found in radioimmunoassay. These latter antisera also stained endocrine cells in the pancreas and intestine with complex cross-reactivity relationships, suggesting the presence of intestinal PP-like peptides in addition to PYY and NPY.