stimulated PGE2 and PGI2 production when the drug was orally administered to normal rats (Ushiyama et al., 1987).
Thus, prostaglandin has a significant role in the pathogenesis of gastric ulceration and serves to maintain normal gastric mucosal integrity (Kleine et al., 1993; Wada et al., 1997). PGE2 is one of the major prostaglandins in gastric tissue. The production of PGE2 is rate-limited by its catalytic enzyme, COX. It has been established that at least 2 forms of COXs exist, termed COX-1 and COX-2. COX-1 is expressed constitutively in most tissues. In contrast, COX-2 expression is usually low under basal conditions. There is increased COX- 2 expression under certain conditions (e.g., inflammation, tissue damage, malignant transformation) (Kargman et al., 1996; Vane and Botting, 1995).