Immunohistochemical localization of human pancreatic polypeptide (HPP) in the human endocrine pancreas

In order to clearly identify the cell type responsible for production of human pancreatic polypeptide (HPP), a newly postulated hormone, we have conducted an immunohistochemical detection of this peptide in the human endocrine pancreas at both light and electron microscopy levels. It was shown that HPP containing cells are located both in endocrine and exocrine pancreatic tissue. In the islets, the positive cells are very few in number and are characterized by an elongated shape and the presence of small secretory granules of about 150 nm in diameter. The presence of HPP in an endocrine cell type reinforce the hypothesis that this peptide is a hormone.