On the metabolism of prostaglandins by human gastric fundus mucosa

Abstract

1. 1. Specific radioimmunoassays for the prostaglandins E 2, F 2α and A 2 and the metabolites 13,14-dihydro-15-keto-prostaglandin E 2, 15-keto-prostaglandin F 2α and 13,14-dihydro-15-keto-prostaglandin F 2α were used to study the metabolism of prostaglandins by gastroscopically obtained small biopsy specimens of human gastric fundus mucosa. 2. 2. Three prostaglandin-metabolizing enzymes were found in the 100000 × g supernatant of human gastric fundus mucosa, 15-hydroxy-prostaglandin-dehydrogenase, Δ 13-reductase and Δ 9-reductase. The specific activity was highest for 15-hydroxy-prostaglandin-dehydrogenase and lowest for Δ 9-reductase. 3. 3. Formation of prostaglandin A 2 (or B 2) was not observed under the same conditions. 4. 4. None of the three enzyme activities detected in the 100000 × g supernatant was found in the 10000 × g and 100000 × g pellets of human gastric fundus mucosa. 5. 5. The results indicate that high speed supernatant derived from human gastric mucosa can rapidly metabolize prostaglandin E 2 and prostaglandin F 2α, to the 15-keto and 13,14-dihydro-15-keto-derivatives. Furthermore, prostaglandin E 2 can be converted to prostaglandin F 2α, the biological activity of which, on gastric functions, differs from that of prostaglandin E 2.