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1. The effects of anti-inflammatory drugs on eicosanoid formation and colonic damage in a chronic model of inflammatory bowel disease (IBD) in the rat were investigated. 2. A single colonic instillation of the hapten, trinitrobenzene sulphonic acid (TNB) resulted in ulceration and inflammation which persisted for 3 weeks. 3. The macroscopic colonic damage, present 3 weeks after TNB, was correlated with an increase in immunoreactive 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and leukotriene B4 (LTB4) synthesis by the rat colon. 4. Anti-inflammatory drugs were administered 2 weeks after TNB, when there was substantial colonic damage, and continued for a week. The experimental drug BW755C inhibited the increased formation of 6-keto-PGF1 alpha and LTB4 by the inflamed colon. Indomethacin and aspirin markedly inhibited prostanoid formation in both inflamed and control colon. Sulphasalazine or prednisolone also inhibited the formation of 6-keto-PGF1 alpha but the effects were less marked. 5. None of the anti-inflammatory drugs significantly reduced the colonic damage induced by TNB. 6. The results suggest that eicosanoids, including LTB4, have only a minor role in maintaining the chronic macroscopic damage induced in the rat colon by TNB. The role of such eicosanoids in the underlying infiltration and activity of inflammatory cells in this model of IBD, however, is not known.

The effects of infusions of bradykinin (0.2 microM), calcium ionophore A23187 (0.5 microM) and arachidonic acid (13 microM) on the release of eicosanoids from the guinea-pig isolated perfused lung were investigated using radioimmunoassay for thromboxane B2 (TXB2), 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), PGE2, leukotriene B4 (LTB4) and LTC4 and bioassay using the superfusion cascade. Bradykinin released more 6-oxo-PGF1 alpha than TXB2, whereas arachidonic acid and ionophore released more TXB2 than 6-oxo-PGF1 alpha. The time course of eicosanoid release varied with the stimulus: bradykinin and arachidonic acid produced an immediate release, whereas the ionophore showed a slower onset of release. Although the amounts of LTB4 and LTC4 released by the ionophore were very low according to radioimmunoassays, there was evidence from the bioassay of release of a leukotriene-like substance, thought to be LTD4. The leukotriene antagonist FPL 55712 lacks specificity in the guinea-pig trachea; at the concentration used (2 microM) it antagonized contractions of the tracheal strip to PGE2 as well as to LTC4. Our results show that in the guinea-pig perfused lung the metabolism of exogenous arachidonic acid is both qualitatively and quantitatively different from the metabolism of endogenous arachidonic acid; furthermore, the profile of eicosanoid production is stimulus-dependent.

1. The effects of oral and subcutaneous administration of the non-steroidal anti-inflammatory drugs sodium salicylate, aspirin and indomethacin on ex vivo gastric mucosal release of leukotriene C4 (LTC4) prostaglandin E2 (PGE2), 6-oxo-PGF1 alpha and thromboxane B2 (TXB2) were investigated in rats under basal conditions as well as after challenge with ethanol. 2. Basal release of PGE2, 6-oxo-PGF1 alpha and TXB2 was inhibited by oral administration of aspirin (0.6-400 mgkg-1) and indomethacin (4 or 20 mgkg-1), but not by sodium salicylate (up to 400 mgkg-1), in a dose-dependent manner. Oral administration of aspirin in the dose range 3.2-400 mgkg-1 and of indomethacin (20 mgkg-1) additionally inhibited release of LTC4, while sodium salicylate (up to 400 mgkg-1) had no effect. Indomethacin (20 mgkg-1) and aspirin (400 mgkg-1) administered subcutaneously inhibited generation of cyclo-oxygenase products of arachidonate metabolism, but did not significantly affect LTC4 synthesis. 3. Oral instillation of ethanol caused gastric mucosal damage and simultaneously induced a selective increase in the ex vivo release of LTC4 from rat gastric mucosa, while release of cyclo-oxygenase products of arachidonate metabolism was not significantly affected. Oral pretreatment of rats with sodium salicylate protected the gastric mucosa and simultaneously inhibited the ethanol-stimulated gastric mucosal LTC4 release in a dose-dependent manner. Sodium salicylate had no effects on the release of PGE2 and TXB2, while that of 6-oxo-PGF1 alpha was slightly increased. 4. Pretreatment with indomethacin (4 or 20mg kg- p.o.) or aspirin in doses up to 25mg kg-1 p.o. prior to oral instillation of ethanol did not inhibit gastric mucosal damage and had no effect on the stimulatory action of ethanol on LTC4 release. Higher doses of aspirin (100mgkg-1 or 400mgkg-1 p.o.) reduced the mucosal damaging effect of ethanol and simultaneously inhibited LTC4 release. 5. The results suggest that aspirin and indomethacin in concentrations higher than those necessary to inhibit the cyclo-oxygenase pathway of arachidonate metabolism additionally inhibit gastric mucosal LTC4 synthesis under basal conditions, while sodium salicylate has no such effect. On the other hand, sodium salicylate, but not indomethacin or low doses of aspirin (up to 25mg kg 1), by an unknown mechanism inhibits stimulation of LTC4 biosynthesis by ethanol and simultaneously protects the gastric mucosa against ethanol-induced damage. Similar effects of high oral doses (> 100mgkg- 1) of aspirin might be due to significant formation of salicylate. These results suggest that there is a causal relationship between enhanced LTC4 biosynthesis and the development of ethanol-induced gastric injury.

The actions of bradykinin on colonic epithelia from essential fatty acid-deficient (EFAD) rats has been examined. Electrogenic chloride secretion as short circuit current (SCC) and release of immunoreactive prostaglandin E2 (iPGE2) and i 6-keto PGF1 alpha have been measured. Resting release of prostanoids was significantly less in EFAD than in control tissues. Bradykinin, in a maximally effective concentration, produced no increase in prostanoid release in EFAD tissues in contrast to controls, while the SCC response was 55% of that in controls. In EFAD tissues the SCC response to bradykinin was the same whether or not the cyclooxygenase inhibitor piroxicam was present. EFAD tissues were not more sensitive to prostaglandins than control tissues. We conclude that while prostaglandin release contributes to the totality of the response to bradykinin, the latter's effect on electrogenic chloride secretion does not require the obligatory production of arachidonic acid metabolites.

1. The time course of mediator release and the hypothesis that the ratio of eicosanoids to histamine might alter with the intensity of stimulus or its route of administration has been explored in isolated perfused lung from sensitized guinea-pigs challenged with ovalbumin. 2. Histamine and prostaglandin release was rapid in onset and virtually complete within 10 min. Thromboxane B2 (TXB2) and leukotriene D4 (LTD4) release, however, was more sustained. Release of the major prostanoid metabolites was relatively delayed compared to that of the parent compounds and was more sustained. 3. Mediator release was antigen-dose dependent and TXB2, prostaglandin D2 (PGD2) and LTD4 release linearly related to histamine concentrations (P less than 0.05). However, the ratio of the percentage maximum release of eicosanoids relative to histamine was greatest with low doses of ovalbumin. 4. At a low antigen dose (10 micrograms ovalbumin), histamine and prostanoid release was greatest when the challenge was via the airway rather than into the pulmonary artery and the greatest differences were in PGF2 alpha levels. At near maximal challenge (1 mg ovalbumin) there was little difference in concentrations of PGD2, TXB2, 6-oxo-PGF1 alpha and LTD4 by either route, but PGF2 alpha levels remained greater. 5. The results indicate that biologically active amounts of prostanoids may be released from sensitized lung at low degrees of mast cell activation and that differences in mediator release following antigen administration to the airway or into the pulmonary vasculature simply reflects its accessibility to sensitized cells.

Guinea-pig gastric mucosal cells isolated by collagenase and pronase digestion were used to study the release of prostanoids prostaglandin I2 (PGI2; measured as 6-keto PGF1 alpha), PGE2, PGF2 alpha and thromboxane A2 (TXA2; measured as TXB2). Lysophosphatide acyltransferase (LAT) and phospholipase A2 (PLA2) were measured in the microsomal fraction of isolated but not separated gastric cells and isolated and enriched parietal and mucous cells. In all cell preparations PLA2 activity was approximately 5 times higher than that of LAT. Acid-activated omeprazole inhibited LAT in a concentration-dependent manner with similar IC50 values in gastric, parietal and mucous cells. It had no effect on PLA2. Gastric cells constantly produced PGI2, PGE2, PGF2 alpha and TXA2. The main prostaglandins released were PGI2 and PGE2. PGF2 alpha and TXA2 were released in smaller quantities. Omeprazole dissolved in polyethylene glycol 400 (PEG) pH 2 inhibited spontaneous PGI2 release in a concentration-dependent manner with an IC50 of 14.3 +/- 4.8 microM. Only concentrations as high as 100 microM produced a significant reduction in PGE2 release by 60%. No significant changes could be detected in the spontaneous release of PGF2 alpha and TXA2. Omeprazole dissolved in PEG pH 7 had no effect on PGI2 release except at 100 microM which led to an insignificant decrease by 40%. These data suggest that omeprazole beyond its inhibitory effect on parietal cell K+/H+-ATPase also affects gastric mucosal prostanoid formation and release. The inhibitory effect on PGI2 does not support the view that omeprazole protects the gastric mucosa by increasing prostanoid formation.

1. Lipid extracts of scale from the lesions of the skin disease psoriasis were purified by high performance liquid chromatography (h.p.l.c.). Assay of fractions by an agarose microdroplet method showed the presence of a novel neutrophil chemokinetic compound which possessed the chromatographic properties of a monohydroxy fatty acid, yet was distinct from the chemoattractant eicosanoid, 12-hydroxyeicosatetraenoic acid, previously isolated in psoriasis. 2. The novel, material, termed compound X, was also detected in fractions collected on h.p.l.c. of extracts of chamber fluid samples obtained from abraded psoriatic lesions, but was not detectable in samples from clinically normal skin. 3. Comparison of the straight and reversed phase h.p.l.c. retention times of compound X with those of a range of standard monohydroxy fatty acids, together with further analysis by gas chromatography-mass spectrometry and assay of selected standards for neutrophil chemokinetic activity, failed to reveal the structural identity of compound X. 4. The finding of a further compound in psoriatic lesions, which stimulates neutrophil movement, highlights the complexity of inflammatory mediator production in this disease.