The epithelia of the respiratory and gastrointestinal tract and their appendages contain a distinct population of disseminated epithelial cells called brush cells or caveolated cells. On the basis of their structure, it was suggested that brush cells might serve as chemo- or volume receptors that play a role in certain aspects of gastrointestinal and bronchopulmonary secretion or motility. In the present study we provide first clues to a possible function of this widespread epithelial cell type. Brush cells of the rat gastric cardia and major pancreatic duct display strong immunoreactivity for nitric oxide synthase (NOS) and also exhibit high activity of NADPH-diaphorase. This NADPH-oxidizing activity was previously shown to be mediated by a specific domain of the sequence of the NOS. NADPH, in turn, appears to be delivered by glucose-6-phosphate dehydrogenase, which we found in brush cells at particularly high levels. We conclude that brush cells of the stomach and pancreas may represent a specialized population of paracrine cells that use nitric oxide as a messenger molecule to control certain gastrointestinal functions.