We have previously shown that the cyclooxygenase (COX)-2/prostaglandin (PG) E2 pathway plays a key role in vascular endothelial growth factor (VEGF) production in gastric fibroblasts. Recent studies have identified three PGE synthase (PGES) isozymes: cytosolic (c) PGES, microsomal (m) PGES-1 and mPGES-2, but little is known regarding the expression and roles of these enzymes in gastric fibroblasts. Thus, we examined IL-1-stimulated mPGES-1 and cPGES mRNA and protein expression in gastric fibroblasts by quantitative PCR and Western blot analysis, respectively; and studied both their relationship to COX-1 and COX-2, and their roles in PGE2 and VEGF production in vitro. IL-1 stimulated increases in both COX-2 and mPGES-1 mRNA and protein expression levels. However, COX-2 mRNA and protein expression were more rapidly induced than mPGES-1 mRNA and protein expression. Furthermore, MK-886, a non-selective mPGES-1 inhibitor, failed to inhibit IL-1-induced PGE2 release at the 8 h time point, while totally inhibiting PGE2 at the later stage. However, MK-886 did inhibit IL- 1-stimulated PGES activity in vitro by 86.8%. NS-398, a selective COX-2 inhibitor, totally inhibited PGE2 production at both the 8 h and 24 h time point, suggesting that COX-2-dependent PGE2 generation does not depend on mPGES-1 activity at the early stage. In contrast, NS-398 did not inhibit VEGF production at 8 h, and only partially at 24 h, while MK-886 totally inhibited VEGF production at each time point. These results suggest that IL-1-induced mPGES-1 protein expression preferentially coupled with COX-2 protein at late stages of PGE2 production, and that IL-1-stimulated VEGF production was totally dependent on membrane-associated proteins involved in eicosanoid and glutathione metabolism (MAPEG) superfamily proteins, which include mPGES-1, but partially dependent on the COX-2/PGE2 pathway.