DMP-777-treated rats show a marked decrease in H/K-ATPase staining parietal cells. DMP-777-induced loss of parietal cells is significantly ameliorated with coadministration of omeprazole. DMP-777-treated animals demonstrates marked foveolar hyperplasia in the fundus with prominent expansion of diastase-resistant, PAS-positive surface mucous cells. When DMP-777 is coadministered with omprazole, there is a significant decrease in BrdUpositive S-phase cells compared with rats that receive DMP-777 alone. After oral dosing of monkeys at 40 mg/kg with DMP-777 the only stereoisomer detected in the post-dose plasma samples is the starting material DMP-777, and no inversion of the configuration at positions 'a' and 'b' of DMP- 777 has occurred in vivo. Mist1-/- mice treated with DMP-777 show fewer chief cell to SPEM transitions. Mist1-/- mice treated with L635 demonstrates significantly fewer proliferative SPEM cells compared to control mice.