PGE2 production is increased in gastric tissues with both acute gastric mucosal lesion and gastric ulcer lesion after administration of plaunotol (Ushiyama et al., 1987; Wada et al., 1997). The administration of a prostaglandin synthesis inhibitor abolishes the inhibitory actions of plaunotol on gastric acid secretion, which indicates that PGE2 has an important role in the gastroprotective effects of plaunotol (Shiratori et al., 1993).