LOCALIZATION OF CONSTITUTIVE ISOFORMS OF NITRIC-OXIDE SYNTHASE IN THEGASTRIC GLANDULAR MUCOSA OF THE RAT

Nitric oxide has been implicated in the regulation of blood flow, muco sal integrity and mucus secretion in the gastric mucosa. An antiserum directed against the C-terminal hexadecapeptide of rat brain nitric ox ide synthase (NOS) and monoclonal antibodies to the neuronal and endot helial forms of NOS were used to establish the location of isoforms of NOS in rat gastric glandular mucosa. Antibodies to the neuronal form of NOS reacted with a band of 160 kDa on immunoblots of brain and gast ric mucosa, and the addition of the hexadecapeptide inhibited recognit ion by the antipeptide antiserum. The antibody to endothelial NOS dete cted a band of 140 kDa on protein blots of samples of intestinal mesen tery and gastric mucosa. Immunohistochemistry using these antibodies d emonstrated that material related to neuronal NOS was present in surfa ce cells of the gastric mucosa, and showed a similar localization to i ntense NADPH diaphorase activity. The antibody to endothelial NOS did not stain the surface of the gastric mucosa but recognized blood vesse ls in the lower region of the gastric glands and in the sub-mucosa. Th is study suggests that nitric oxide might act both as an intra- and in ter-cellular messenger to regulate mucus release, and that the NOS pre sent in surface cells is related more closely to the neuronal than to the endothelial isoform.