Sequential expression of adrenomedullin and its receptor during gastric ulcer healing in rats

Adrenomedullin (AM) is a potent vasodilatory peptide. While its growth-regu lating action in some cultured cells has been recognized, expression of AM and its receptor during gastric ulcer healing has not been explored. Specim ens of gastric walls from control rats or gastric ulcers were obtained at 1 , 3, 7, and 14 days after gastric ulcer induction. AM and its receptor mRNA s expression were determined by reverse transcription-polymerase chain reac tion (RT-PCR) and in situ hybridization. By RT-PCR, AM mRNA was increased b y 167% at three days, while AM receptor mRNA was increased by 234% at seven days (both P < 0.05). By in situ hybridization, AM and AM receptor mRNAs w ere increased at ulcer margin from three days after ulcer induction. By imm unohistochemistry, AM was increased in the ulcer margin at three and seven days. In separate in vitro studies using a rat gastric epithelial (RGM1) ce ll line, AM treatment significantly increased transforming growth factor-cw mRNA expression and cell proliferation.