Effect of monochloramine on recovery of gastric mucosal integrity and blood flow response in rat stomachs — Relation to capsaicin-sensitive sensory neurons

Abstract

Gastric mucosal blood flow (GMBF) response and the recovery of gastric mucosal integrity were investigated in anesthetized rat stomachs after damage by monochloramine (NH2C1), in comparison with 20 mM taurocholate Na (TC). A rat stomach was mounted in an ex-vivo chamber, and the mucosa was exposed to 50 mM HCl during a test period. Mucosal application of 20 mM TC for 10 min caused a marked reduction of transmucosal potential difference (PD), but the PD recovered rapidly without development of gross lesions 90 min later. In contrast, the exposure of the mucosa to NH 2Cl (5~20 mM) produced a concentration-dependent decrease in gastric PD, and the values remained lowered even 90 min after removal of the agent, resulting in severe hemorrhagic damage in the stomach. TC caused a considerable H + back-diffusion, followed by an increase in the GMBF. In the mucosa damaged by NH 2Cl, such GMBF responses were not observed, except for the temporal increase during the exposure, although similar degrees of H + back-diffusion were observed following NH 2Cl treatment. In addition, the prior exposure of the mucosa to NH 2Cl significantly attenuated gastric hyperemic response induced by capsaicin but not by misoprostol (a PGE 1 derivative) or NOR-3 (a NO donor). Chemical ablation of capsaicin-sensitive sensory neurons had no effect on the PD reduction caused by TC but totally attenuated the GMBF response, resulting in hemorrhagic damage in the stomach. These results suggest that NH 2Cl delayed the recovery of the mucosal integrity in the stomach after damage, and this effect may be attributable, at least partly, to the impairment of gastric hyperemic response associated with H + back-diffusion, probably due to dysfunction of capsaicin-sensitive sensory neurons.