Porcine diazepam-binding inhibitor is immunohistochemically colocalized with somatostatin in the D cells of human and porcine gastrointestinal tract and in pancreatic islet cells.

Abstract

The cellular distribution of a novel porcine peptide, diazepam-binding inhibitor (DBI), was immunohistochemically mapped in the human and porcine gastrointestinal tract and pancreas. Using a rabbit antiserum, raised against porcine DBI, immunoreactive epithelial cells were found in the gastric antrum and duodenal mucosa and in the parenchymal cells of the islets of Langerhans of both species. The immunoreactivity could not be absorbed by high concentrations of insulin, somatostatin (SS-14, SS-28), glucagon, or pancreatic polypeptide but was abolished by porcine DBI. Using semithin, consecutive sections, the immunoreactive intestinal and islet cells were found to be identical to the somatostatin-producing D cells. Since it has been shown that porcine DBI interferes with the secretion of insulin, the peptide may act as a modulator of islet hormone release, possibly in a paracrine manner.