Increased metabolism of arachidonic acid in an immune model of colitis in guinea‐pigs

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Abstract
1 Inflammation of the guinea-pig colon was produced by skin sensitization and subsequent intracolonic challenge with the chemical hapten, dinitrochlorobenzene. 2 Metabolism of [14C]-arachidonic acid by homogenates of control colon was very low, although metabolites co-migrating on thin layer chromatography (t.l.c.) with prostaglandin E2 (PGE2), PGF2α, PGD2, 6-keto-PGF1α, thromboxane B2 (TXB2), HHT and 11-, 12-, 15-HETE were formed. 3 There was an overall 3 fold increase in metabolism of [14C]-arachidonic acid by homogenates of inflamed mucosa. The greatest increase in metabolite formation was of PGE2, with smaller increases in HHT, 11-, 12-, 15-HETE, PGD2, TXB2, PGF2α and 6-keto-PGF1α. The formation of these metabolites was inhibited both by indomethacin and the dual pathway inhibitor, BW755C. 4 The formation of immunoreactive PGE2, TXB2 and 6-keto-PGF1α was also increased in homogenates of inflamed guinea-pig colon. The small level of immunoreactive LTB4 detected in control colon was not changed in inflamed colonic tissue. 5 The dinitrochlorobenzene model of colitis offers a means of studying arachidonic acid metabolism in an immune-mediated inflammatory response in intestinal tissue.