Exacerbatory mechanism responsible for water immersion stress-induced gastric lesions in aged rats compared with young rats.

1. The present study was designed to investigate whether or not ageing affects the development of water immersion stress-induced gastric lesions in rats. Effects of cetraxate, an anti-ulcer drug, were also examined. 2. Gastric lesions were induced by 6 h water immersion stress in rats. Gastric mucosal blood flow was determined by the hydrogen gas clearance technique and nitric oxide synthase (NOS) activity was measured enzymatically. 3. Early development of gastric lesions was observed in aged rats and exacerbation of gastric lesions was also found. Lowering of gastric mucosal blood flow and reduced NOS activity were observed in aged rats. 4. Cetraxate mitigated the development of gastric lesions in young rats and also increased gastric mucosal blood flow and NOS activity. However, these favourable effects were diminished in aged rats. 5. Decreased NOS activity may be an important exacerbatory factor to the development of gastric lesions in aged rats. 6. Effects of cetraxate differed between young rats and aged rats. 7. These results may explain the refractoriness and drug resistance in gastric ulcers encountered by elderly individuals.