Short term effects of indomethacin on rat small intestinal permeability. Role of eicosanoids and platelet activating factor.

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Abstract
Short term effects of indomethacin on intestinal permeability were studied on a model of rat isolated vascularly perfused terminal ileum. The objectives of this study were (a) to assess the effects of indomethacin on intestinal permeability and histology; (b) to assess the effects of prostaglandins, leukotrienes, and platelet activating factor (PAF) on the same parameters; (c) to evaluate the role of these inflammation mediators on indomethacin induced permeability modifications. Intravascular administration of 1.25 and 2.5 mM indomethacin induced a significant increase of 51Cr-EDTA transfer rate. Histological analysis showed only mucosal oedema. Pretreatment with 16,16 dimethyl-prostaglandin E2 did not reverse these changes. Intravascular administration of PAF, leukotrienes B4 and D4 provoked a significant rise in 51Cr-EDTA transfer rate and intraluminal protein leakage, with an intense vascocongestion of the mucosal capillaries. These changes were completely prevented by perfusion of the respective specific antagonists (BN52021 for PAF, LY255,583 for leukotriene B4 and MK571 for leukotriene D4). None of these three antagonists, however, or MK886, a selective 5'-lipo-oxygenase inhibitor, could reverse the indomethacin induced permeability changes. Indomethacin induced increased intestinal permeability at these high concentrations does not seem to be a result of changed prostanoid or PAF metabolism. Alternative mechanisms of the initial damage of non-steroid anti-inflammatory drugs should be sought.