Adaptive cytoprotection: an endoscopic study in man.

We studied the protective effect of the mild irritant 20% ethanol against the damage caused by the strong irritant 40% ethanol to the duodenal mucosa of 10 healthy volunteers. At time 0, placebo (1% ethanol) or 20% ethanol (6 ml) was sprayed directly onto the duodenal wall through an endoscope. After 15 min 40% ethanol (50 ml) was given; damage was assessed by endoscopic examination 30 min after ethanol. The damage was scored arbitrarily: score 0, no damage; 1, duodenal hyperemia; 2, one hemorrhagic lesion; 3, two to five hemorrhagic lesions; 4, five hemorrhagic lesions. In separate experiments, the effect of acetylsalicylic acid (20 mg/kg iv) on adaptive cytoprotection was evaluated. It was found that 1) 20% ethanol does not damage the duodenal mucosa, whereas 40% ethanol does; 2) duodenal hyperemia and hemorrhagic lesions caused by 40% ethanol can be prevented by the previous administration of 20% ethanol; and 3) acetylsalicylic acid does not damage the duodenal mucosa but abolishes the protective effect of 20% ethanol. "Adaptive cytoprotection" is a physiological phenomenon in humans too and further supports the probable defensive role of endogenous prostaglandins in the gastrointestinal tract.