Detection of nitric oxide synthase (NOS) in somatostatin-producing cells of human and murine stomach and pancreas

The aim of this study was to identify by immunocytochemistry the distribution of nitric oxide synthase (NOS) in human and murine gastric epithelium. Using two different antisera specific for neuronal NOS (nNOS), we detected nNOS immunoreactivity in endocrine cells of the epithelium of the body and pyloric regions as well as in ganglion cells of the intrinsic plexi of the stomach of the three species studied. Both immunocytochemistry of contiguous sections and double immunolabeling methods showed that the nNOS-immunoreactive cells were also immunoreactive for somatostatin. Co-localization of nNOS and somatostatin has also been found in the pancreatic islets, where strong nNOS immunoreactivity appeared in scattered cells, which were peripheral in rat and mouse islets and more randomly distributed in human. The possibility of crossreactivity between the antisera against nNOS and somatostatin was ruled out by means of absorption controls. Immunocytochemical techniques were also applied to thin sections, confirming the immunostaining of gastric D-cells, which was restricted principally to the secretory granules. The possible functional implications of these findings for gastric and pancreatic physiology are discussed.