Adrenomedullin (AM) is a potent vasodilatorypeptide, which is present in the stomach. However, itsprecise function in the gastric mucosa is unknown. Theexpression and localization of AM and its receptor in gastric mucosa injured by ethanol also havenot been explored, forming the basis for this study.Gastric samples of rats were obtained at 0 and 8 hr and1, 2, and 4 days after intragastric administration of 100% ethanol. By RT-PCR, AM mRNA expressionin gastric mucosa at 8 and 24 hr following ethanolinjury was increased by 2-fold and by 2.5-fold (both P< 0.01), respectively, and returned to normal at two days. AM receptor mRNA expression wasincreased by 2.7-fold, 2.3-fold, and 2.4-fold at 8, 24,and 48 hr, respectively (all P < 0.01), and returnedto normal at four days. By in situ hybridization, AM and AM receptor mRNAs were present in normalgastric mucosa and up-regulated in gastric mucosafollowing ethanol injury. The immunohistochemical signalfor AM was significantly increased in the mucosa bordering erosion sites. We conclude thatethanol injury up-regulates the expression of both AMand AM receptor in gastric mucosa.