Effect of 2'-carboxymethoxy-4,4'-bis(3-methyl-2-butenyloxy)chalcone (SU-88) on prostaglandin metabolism in hog gastric mucosa.

SU-88 [2'-carboxymethoxy-4,4'-bis(3-methyl-2-butenyloxy)chalcone] inhibited the activity of the prostaglandin (PG)-metabolizing enzyme, 15-hydroxy-PG-dehydrogenase (15-OH-PG-DH), in a cytoplasmic fraction of gastric mucosa. This compound had no effect on the PG synthetase of bovine seminal vesicle microsomes and lactate dehydrogenase in rat liver. The 15-OH-PG-DH activity of gastric mucosa was not influenced by a specific inhibitor of alcohol dehydrogenase, 4-methylpyrazole. Carbenoxolone (CBX) also inhibited 15-OH-PG-DH activity. The IC50 values for SU-88 and CBX were approximately 20 and 40 microM respectively. SU-88 inhibited 15-OH-PG-DH activity uncompetitively or competitively according to whether PGE1 or NAD was used as substrate. CBX inhibited competitively the activity of this enzyme for both substrates. After the addition of SU-88 or CBX to the incubation medium of gastric mucosa, the PGE2 level of the medium was increased significantly while that of the tissue remained unchanged. These results indicate that SU-88 specifically inhibited 15-OH-PG-DH activity and suggest that 15-OH-PG-DH activity regulates the level of PGs in gastric mucosa and may have an anti-ulcer influence.