The role of luminal factors in prostaglandin protection against ethanol‐induced gastric mucosal injury

Prostaglandins (PG) protect the gastric mucosa against damage by several irritants, but the mechanisms remain unclear. A standard rat model of gastric injury induced by 50% ethanol was used to test the hypothesis that PG protection occurs either by increasing luminal fluid volume and hence diluting the irritant, or by production of protective factors within this fluid. Quantitative histology was used to asssess microscopic mucosal damage. The increase in luminal fluid volume in prostaglandin E2 (PGE2)‐treated animals was measured, and the ability of this increased fluid to protect saline‐treated animals via dilution of the irritant was assessed. The transfer of protection by exchange of luminal fluid from PG to non‐PG treated animals was also tested. Results showed that PGE2 induced a specific increase in luminal fluid volume of 45.6%. When given together with ethanol treatment the extra fluid volume was not protective. Removal of luminal fluid after PG and before ethanol treatment did not abolish protection and no protective factor was transferred with the luminal fluid. In conclusion, this study has shown that neither dilution of ethanol by accumulation of luminal fluid nor the presence of luminal factors is responsible for PG protection.