RELATIONSHIP BETWEEN CONSTITUTIVE NITRIC OXIDE SYNTHASE ACTIVITY AND MUCUS LEVEL IN THE GASTRIC MUCOSA OF RATS WITH STRESS

A decrease in constitutive nitric oxide synthase (cNOS) activity occurred with decreases in hexosamine (an index of mucus synthesis) and adherent mucus (an index of mucus secretion) concentrations in the gastric mucosa of rats with water immersion restraint (WIR) stress. The decreases in gastric mucosal hexosamine and adherent mucus concentrations were enhanced with a further decrease in gastric mucosal cNOS activity by pretreatment withNG–monomethylL-arginine, a non-selective NOS inhibitor, but were prevented with maintenance of the gastric mucosal cNOS activity by pretreatment with aminoguanidine, a selective inducible NO synthase inhibitor. In all WIR-stressed rats used in this study, gastric mucosal cNOS activity was well correlated with either gastric mucosal hexosamine or adherent mucus concentration (r=0.717 or 0.739, respectively). These results indicate that in the gastric mucosa of WIR-stressed rats, a decrease in cNOS activity is closely related to a decrease in mucus level due to impairment of its synthesis and secretion.