PEPTIDE-YY - A NEUROPEPTIDE IN THE GUT - IMMUNOCYTOCHEMICAL AND IMMUNOCHEMICAL EVIDENCE

Peptide YY immunoreactivity was detected in neuronal elements in the u pper digestive tract of the rat, cat, ferret and pig by immunocytochem istry and radioimmunoassay combined with high-performance liquid chrom atography. The two peptide YY antisera used do not recognize the relat ed peptides neuropeptide Y and pancreatic polypeptide. In the rat pept ide YY-immunoreactive nerve fibres were virtually restricted to the st omach smooth muscle of the minor curvature where they were numerous. P eptide YY-immunoreactive nerve cell bodies occurred in small ganglia o n the serosal surface of the minor curvature. In the cat and ferret pe ptide YY-immunoreactive nerve fibres occurred in the circular smooth m uscle layer of both the minor and major curvatures of the stomach and also in the upper small intestine; such fibres were numerous also in m yenteric ganglia in these regions. In the pig, they were few but had r oughly the same distribution as in the cat and ferret, except that the y were quite numerous in thick muscle bundles close to the oesophagoga stric junction. The presence of peptide YY-immunoreactive nerve cell b odies within the myenteric ganglia along the upper digestive tract of cat, ferret and pig, and in serosal ganglia of the rat stomach, indica tes that at least some of the peptide YY-immunoreactive fibres demonst rated originate in or close to the gut wall. Double-staining experimen ts revealed that virtually all peptide YY-containing neurons and nerve fibres were distinct from those storing neuropeptide Y. Peptide YY-im munoreactive endocrine cells were encountered not only in the lower in testines but also in the stomach of the four species studied. In the a ntrum such cells were numerous and constituted a subpopulation of the gastrin-containing cells. In the oxyntic mucosa they were few and cont ained somatostatin. Radioimmunoassay revealed peptide YY-like peptides in gastric mucosa and smooth muscle from the upper digestive tract of all four species examined. The results of high-performance liquid chr omatography suggest that the peptide YY-like material in the upper dig estive tract is distinct from neuropeptide Y and pancreatic polypeptid e and identical with authentic peptide YY except in the antral mucosa where only a small proportion of the peptide YY-immunoreactive materia l eluted like authentic peptide YY.