IMMUNOCYTOCHEMICAL LOCALIZATION OF THE NPY PYY Y1 RECEPTOR IN THE DEVELOPING PANCREAS/

Neuropeptide Y, peptide YY, and pancreatic polypeptide are structurall y related peptides that are considered to play a role in the regulatio n of pancreatic secretion and blood flow. Several receptor subtypes fo r these peptides have been identified, and the Y1, Y2, Y4/PP1, Y5, and Y5/PP2/Y2b receptors are cloned. We have prepared polyclonal peptide antibodies that recognize the Y1 receptor and now report on its locali zation in the adult and developing rat pancreas. In the adult pancreas , Y1 receptors were detected both in some centroacinar and intralobula r duct cells and in endothelial cells. In the developing pancreas (E12 .5-E16.5), Y1 receptor immunoreactivity was observed in numerous nonen docrine epithelial cells. These cells occurred in the immediate vicini ty of peptide YY-positive endocrine cells. At E16.5, a fraction of the se Y1 receptor-containing cells co-stored amylase. One day later, Y1 r eceptor immunoreactivity became restricted to pancreatic duct-like cel ls that occurred in close proximity to peptide YY cells. In fetal rats , intense Y1 receptor staining was also observed in endothelial cells. These observations, together with the finding of early pancreatic pep tide YY expression, suggest that peptide YY produced by fetal endocrin e cells may exert an action on exocrine cells, duct cells and endothel ial cells during development.