Effect of Topically Applied Cyclooxygenase-2-Selective Inhibitors on Arachidonic Acid- and Tetradecanoylphorbol Acetate-Induced Dermal Inflammation in the Mouse

The topical effects of cyclooxygenase-2 (COX-2)-selective inhibitors, flosulide (CGP 28238), L-745,337 and SC-57,666 were examined in AA- and TPA-induced ear dermal inflammation in the mouse. The doses that caused 50% inhibition in AA edema (ED₅₀) were 2.4, 0.45 and 0.35 mg/ear for flosulide, L-745,337 and SC-57,666, respectively. The respective ED_50s in TPA-edema were 1, 0.45 and 0.14. Indomethacin and zileuton showed higher activity than the COX-2-selective inhibitors in both models. Flosulide and L-745,337 inhibited the AA-induced increase in 6-keto-PGF₁, while SC-57,666 was inactive. 80% inhibition was seen with indomethacin while zileuton had no effect. COX-2 selective inhibitors and indomethacin had no effect on LTB₄ levels, while zileuton produced a 50% inhibition. The TPA-induced increase in 6-keto-PGF₁ was greatly inhibited by all COX-2 inhibitors while LTB₄was potentiated by both flosulide and L-745,337. Indomethacin inhibited 6-keto-PGF₁ and zileuton reduced 6-keto-PGF and strongly reduced LTB₄. The neutrophil influx induced by AA was lower than that of TPA. Myeloperoxidase (MPO) levels were lowered by flosulide and L-745,337 but not by SC-57,666. TPA-induced MPO increase was decreased by all COX-2 inhibitors. Indomethacin and zileuton had similar effect on AA and TPA-induced increase in MPO. The results indicate that COX-2-selective inhibitors showed lower topical anti-inflammatory activity than indomethacin or zileuton.     

Acute Effects of the Anti-Inflammatory Cyclooxygenase-2 Selective Inhibitor, Flosulide, on Renal Plasma Flow and Glomerular Filtration Rate in Rats

Nephrotoxicity of nonsteroidal anti-inflammatory drugs is associated with other risk factors (volume-depletion) and may be secondary to functional changes mediated by the inhibition of renal cyclooxygenases. Acute anti-inflammatory doses of flosulide and indomethacin were determined on carrageenan paw edema and its effects on renal plasma flow (RPF) and glomerular filtration rate (GFR) were studied in normovolemic and hypovolemic rats. In normovolemic rats, flosulide increased RPF and GFR (25 mg/kg) and indomethacin (5–10 mg/kg) was without effect. Volume-depleted rats were obtained by oral furosemide (32 mg/kg), urinary eicosanoids were determined. After furosemide, plasma volume, RPF and GFR and PGE₂ decreased. Treatment of hypovolemic rats with flosulide (5–25 mg/kg) or indomethacin 10 mg/kg reduced RPF and GFR. Flosulide at 5 mg/kg reduced 6-keto-PGF₁ whereas at 25 mg/kg and after indomethacin at 10 mg/kg a fall in 6-keto-PGF₁ and TXB₂ appeared. Our data suggest that acute COX-2 selective inhibition may alter renal function.     

Sulphasalazine and experimental stress ulcers

The effects of sulphasalazine on gastric ulceration induced by restraint at 4°C (stress) for 2 h were studied in rats. Doses of 63 or 125 mg/kg s.c., which had no effect on stomach wall prostaglandin E₂ (PGE₂) levels, prevented stress ulceration but not the lesions produced by indomethacin. Stress significantly increased gastric glandular mucosal PGE₂ levels. Indomethacin pretreatment (20 mg/kg, p.o.) markedly reduced PGE₂ levels in the same region of the stomachs, and worsened stress-induced lesion formation. Pretreatment with sulphasalazine of animals given indomethacin and then subjected to stress did not appear to affect the indomethacin component of indomethacin-stress ulceration. Oral administration of PGE₂ 200 g/kg significantly elevated gastric PGE₂ levels, but had no effect on stress ulceration.It appears that neither the antiulcer activity of sulphasalazine nor stress-induced ulceration is associated with gastric tissue PGE₂ increase or decrease, respectively. The protective mechanism may result from the ability of sulphasalazine to inhibit lipoxygenase activity.     

The effect of ebselen on polymorphonuclear leukocyte migration to joints in rats with adjuvant arthritis

We have previously reported that ebselen (PZ 51,2-Phenyl-1,2-Benzoisoselenazol-3-(2H)-one), a selinyl organic compound with anti-inflammatory properties, inhibited human polymorphonuclear leukocyte (PMNL) adhesion to and migration through cytokine-activated human umbilical vein endothelium in vitro. Here we investigated the in vivo effect of ebselen on PMNL migration into arthritic joints and dermal inflammation in rats with adjuvant arthritis. The rats were immunized with adjuvant (Mycobacteriaum butyricum in mineral oil) and 13 days later, when arthritis was fully developed, treatment (p.o.) with ebselen, indomethacin or vehicle was initiated. The migration of ⁵¹Cr-labelled blood PMNL purified from arthritic donors and extravasation of ¹²⁵I-labelled HSA in arthritic joints and dermal inflammatory reactions was quantitatively measured. Treatment of rats with 100 mg/kg/day ebselen for 3 days, inhibited by 72–79% the PMNL migration into arthritic joints and tail (spondylitis) and by 50–60% into dermal inflammatory reactions induced with zymosan-activated rat serum (ZAS; C5a_desArg), endotoxin (LPS) or IL-1α. The inhibitory effect of ebselen was dose-dependent, because treatment of rats with 100 mg/kg/day ebselen caused significantly more inhibition of PMNL migration than did 30 mg/kg/day, although this dose was still effective. Ebselen inhibited PMNL migration into arthritic joints and dermal inflammation within 3 h of initial oral administration (100 mg/kg). However, ebselen did not suppress plasma albumin extravasation into arthritic joints and dermal inflammatory reactions. Compared to ebselen, treatment with indomethacin (2 mg/kg/day) was significantly less effective in inhibiting PMNL accumulation in joints, but in contrast to ebselen, indomethacin did inhibit plasma albumin extravasation into carpal and talar joints. The results suggest that ebselen effectively and rapidly inhibits PMNL migration in vivo, as also observed in vitro, and that it has anti-inflammatory actions distinct from classic nonsteroidal anti-inflammatory drugs such as indomethacin.     

Effects and mechanisms of Paeoniflorin,a bioactive glucoside from paeony root,on adjuvant arthritis in rats

Objective and design: Paeoniae alba Radix has been recognized as a valuable herb in the treatment of rheumatoid arthritis (RA) in traditional Chinese medicine. The purpose of this study was to investigate the effects of Paeoniflorin (PF), a bioactive glucoside from paeony root, on the rats with adjuvants arthritis (AA) and underlying mechanisms. Materials: AA was induced by injecting Complete Freund’s adjuvant (10 mg/ml) into hind paw in male Sprague-Dawley rats. Treatment: PF (5, 10, 20 mg/kg/d) was orally administered to the rats 14 to 20 days after injection of complete Freund’s adjuvant. Methods: Arthritis was evaluated by hind paw swelling, polyarthritis index, immune organ weights, and histological examination. Interleukin-1 (IL-1) activity was assessed by thymocyte proliferation as quantified by the 3-(4, 5-2dimethylthiazal- 2yl) 2,5-diphenyltetrazoliumbromide (MTT) assay. The content of prostaglandin E₂ (PGE₂) was measured by radioimmunoassay. The levels of IL-6, granulocyte macrophage colony stimulating factor (GM-CSF) and vascular epidermal growth factor (VEGF) in synovium homogenates were measured by enzyme-linked immuno-absorbent assay (ELISA) respectively. Expression of inhibitory subunits of G protein (G i) and cyclo-oxygenase-2 (COX-2) were detected by Western blotting technique. Results: There were significant secondary inflammatory reactions in AA rats, which were accompanied by a decrease in immune organ weights. The administration of PF (10, 20 mg/kg/day, i. g., days 14–20) inhibited the inflammatory response and restored the weight of immune organs of AA rats. Synoviocyte proliferation of AA rats increased significantly, and the levels of IL-1, PGE₂, IL-6, VEGF and GM-CSF in synovial homogenates of AA rats were also elevated compared with the normal group. The administration of PF (10, 20 mg/kg/day, i.g., days 14–20) reduced the above changes significantly. Finally, the expression of Gi1, Gi2, Gi3 and COX-2 in synovial homogenates of AA rats were also elevated. The administration of PF reduced Gi expression at doses of 10 and 20 mg/kg and decreased COX-2 expression at a dose of 20 mg/kg. Conclusion: PF suppresses rat AA at least partly by inhibiting abnormal proliferation of synoviocytes and the production of IL-1, PGE₂, IL-6, VEGF and GM-CSF by synoviocytes and reducing Gi and COX-2 expression in synovium. Received 3 January 2006; returned for revision 22 May 2006; returned for final revision 23 August 2006; accepted by M. Parnham 8 November 2006     

Immunological abnormalities in rats with adjuvant-induced arthritis--II. Effect of antiarthritic therapy on immune function in relation to disease development

The effects of the experimental immunomodulatory agent tilomisole (Wy-18,251; (3-(p-chlorophenyl) thiazolo [3,2-a]benzimidazole-2-acetic acid) on disease development and immune function in rats with adjuvant-induced arthritis was assessed in comparison with indomethacin and levamisole. Daily p.o. administration of tilomisole (100-200 mg/kg/day) to M. butyricum-injected rats significantly reduced both edema and bone erosion in the uninjected paw. Moreover, tilomisole treatment restored to normal the diminished Con A-induced proliferative response and IL 2 synthesis observed in spleen cells from arthritic rats, but had no effect on macrophage IL 1 production. In contrast, levamisole treatment (25 mg/kg/day) of arthritic rats improved splenic immune function but did not influence paw edema or bone erosion. Conversely, indomethacin (1 mg/kg/day) significantly reduced paw edema and bone erosion but did not improve the deficient proliferative response or IL 2 synthesis by "arthritic" spleen cells. These results indicate that tilomisole possesses combined antiinflammatory and immunomodulatory activity in adjuvant-arthritic rats which is distinctly different from the effects of either indomethacin or levamisole. Moreover, these data suggest that tilomisole has potential disease-modifying activity in arthritis, which is currently being more closely examined in clinical trials.     

Release of 15-hydroxy-5,8,11,13-eicosatetraenoic acid and cysteinyl-leukotrienes in carrageenin-induced inflammation: Effect of non-steroidal anti-inflammatory drugs

Inflammatory exudates obtained in rats after subcutaneous implantation of carrageenin-soaked sponges were found to contain relatively large amounts of 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) and smaller amounts of cysteinyl-leukotrienes (LT) in addition to LTB₄, thromboxane (TX) B₂ and prostaglandin (PG) E₂. Concentrations of 15-HETE and cysteinyl-LT were high 5 hours after sponge implantation and decreased significantly within 24 hours. This time-course, which is smilar to that of TXB₂, but differs from that of PGE₂, suggests migrating leukocytes as a major source of 15-HETE and cysteinyl-LT. Aspirin, sodium salicylate, dipyrone (100 mg/kg each) and indomethacin (2 and 20 mg/kg) decrease the concentrations of cyclooxygenase products of arachidonate metabolism, but did not significantly affect levels of 15-HETE. Cysteinyl-LT were increased by 20 mg/kg indomethacin, but remained unaffected by 2 mg/kg indomethacin and by the other non-steroidal anti-inflammatory drugs (NSAID) tested. 15-HETE and cysteinyl-LT could play a mediator role in inflammation. In addition, they could modulate the release and effects of other inflammatory mediators.     

Efflux of cyclic AMP,prostaglandin E2 and F2 and thromboxane B2 in leg lymph of rabbits after scalding injury

Leg lymph was collected from pentobarbital anaesthetized rabbits before and after scalding injury of the paw (75°C for 20 s), and the contents of cyclic AMP (cAMP), prostaglandin E₂ (PGE₂) and PGF_2α and thromboxane B₂ (TXB₂) in lymph were determined. After injury lymph flow increased about four times. The maximal rate of flow was found between 30 and 60 min after scalding. The efflux of cAMP and immunoreactive iPGE₂, iPGF_2α and iTXB₂ also increased. The maximum values were detected at approximately 0–30, 30–60, 30–60 and 180–240 min, respectively, after the injury. The output of cAMP, iPGE₂ and iPGF_2α and iTXB₂ in lymph of the contralateral non-scalded paw remained low throughout the experiments. When rabbits were injected with indomethacin (2.5 mg/kg) or diclofenac sodium (2.5 mg/kg) immediately after the scalding injury, the efflux of cAMP, iPGE₂ and iPGF_2α were low. Lymph flow was markedly reduced after treatment with diclofenac sodium; treatment with indomethacin did not significantly affect lymph flow. The results suggest a prostaglandin-dependent formation of cAMP following scalding injury which may be related to the initial responses to scalding.     

Relationship of blood markers to disease severity and drug efficacy in rat adjuvant arthritis

Rat adjuvant arthritis (AA) was used as a model to evaluate several blood markers as possible predictive indicators of drug efficacy. AA was induced in Sprague-Dawley rats by the injection of complete Freund's adjuvant into the right hind foot pad. The rats were dosed p.o. from day 18 to day 31 with levamisole (10 mg/kg), indomethacin (1 mg/kg), diclofenac sodium (0.5 & 1 mg/kg), and prinomide (10 & 20 mg/kg). Disease severity was assessed by paw circumference on day 31. The following blood markers were analyzed: hyaluronate by ELISA, prostaglandin E₂ by RIA, ESR by micro-dispette, total PMN by Technicon H-1, and albumin by BCG dye. Blood marker correlation (r) to disease severity was: hyaluronate (0.71), prostaglandin E₂ (0.58), ESR (0.52), PMN (0.58), and albumin (–0.71). The relative rank order of drug efficacy (indomethacin, diclofenac sodium, and prinomide) did not differ using the change in paw circumference (day 31–day 17) or blood markers. Levamisole exacerbated the disease as measured by all the above parameters. Thus, these blood markers provide additional information for the statistical evaluation of drugs in rat adjuvant arthritis.     

Effects of a COX-2 Preferential Agent Nimesulide on TNBS-Induced Acute Inflammation in the Gut

In inflammatory bowel disease, increased production of prostaglandins by cyclooxy- genase-2 (COX-2) contributes to bowel dysfunction, inflammatory edema, and hyperemia suggesting that inhibitors of COX-2 may have beneficial effect in gut inflammation. We compared the effects of nimesulide, a preferential COX-2 inhibitor, with those of indomethacin, acetylsalicylic acid (ASA), and dexamethasone in a 24-h model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in the rat. TNBS-induced colitis was associated with enhanced COX-2 expression in the gut and increased circulating concentrations of PGE₂ metabolite (PGEM). Treatment with nimesulide (10 mg/kg), indomethacin (10 mg/kg), or dexamethasone (1 mg/kg) reduced plasma PGEM concentrations and edema in the inflamed bowel. In addition, nimesulide and dexamethasone treatments decreased neutrophil infiltration into the inflamed colon mucosa. ASA (10 mg/kg) did not have a significant effect on any of these measures of inflammation. None of the studied drugs reduced the size of inflammatory mucosal lesions in the colon. In TNBS-induced acute inflammation of the colon, nimesulide reduced the formation of inflammatory edema, probably by a mechanism related to inhibition of PGE₂ production by COX-2 pathway. In addition, nimesulide inhibited neutrophil infiltration into inflamed mucosa mimicking the action of dexamethasone.     

Efficacy of <Emphasis Type="Italic">Bacopa monniera</Emphasis> (L.) Wettst in Alleviating Lysosomal Instability in Adjuvant-Induced Arthritis in Rats

The present study was aimed to assess the effect of Bacopa monniera extract against lysosomal instability during adjuvant-induced arthritis in rats. B. monniera extract was administered orally at a dose of 100 mg/kg body weight for 30 days to the experimental rats after the induction of adjuvant arthritis. The ability of B. monniera extract to stabilize lysosomal enzyme activities in the cartilage of control and experimental rats was done by monitoring the activities of pathophysiological enzymes such as β-glucuronidase, β-glucosaminidase, cathepsin D, hyaluronidase, collagenase and the level of protein bound carbohydrates and glycosaminoglycans (GAGs) in arthritic rats. B. monniera extract supplementation significantly inhibited lysosomal instability in different tissues studies and improved the level of glycoproteins in synovial effusate and GAG in the cartilage. To evaluate whether anti-inflammatory property of B. monniera extract was due to lysosomal stability and GAG protection, purified chloroform fraction of B. monniera (CF) was assayed for its role to modulate interleukin-6 (IL-6) expression and prostaglandin E₂ (PGE₂) production. Administration of CF (50 mg/kg) to arthritic rats significantly downregulated the expression of IL-6 in blood mononuclear cells and PGE₂ levels in cartilage tissue. The possible mechanism of action of the B. monniera extract may be through its stabilizing action on lysosomal membranes and hence the decrease in spread of inflammation.     

Anti-inflammatory effect of quinoline alkaloid skimmianine isolated from Ruta graveolens L.

Objective

The present study evaluates the anti-inflammatory effect of the quinoline alkaloid skimmianine (SKM), isolated from Ruta graveolens L., against carrageenan-induced acute inflammation.

Methods

SKM at a dose of 5.0 mg/kg body weight was found to be the minimal concentration for maximal edema inhibition. Carrageenan suspension was administered into the sub-plantar tissue of the right hind paw 1 h after SKM and diclofenac (20 mg/kg) administration (i.p.). Paw edema was determined 3 h after carrageenan administration. The rats were then killed and mRNA expressions of TNF-α and IL-6, levels of PGE₂ and TBARS, activities of COX-2, 5-LOX, SOD, catalase, glutathione peroxidase (GPx) and myeloperoxidase (MPO) and the level of nitrite were measured.

Results

SKM treatment resulted in a decrease in the mRNA levels of TNF-α and IL-6, which are upstream events of the inflammatory cascade. The levels of PGE₂ and NO and the activities of COX-2 and 5-LOX were also significantly reduced after SKM treatment. Neutrophil infiltration, lipid peroxidation and associated oxidative stress in the paw tissue were reduced following SKM treatment.

Conclusion

These results support the anti-inflammatory properties of skimmianine and its multi-targeted mechanism of action, suggesting its potential therapeutic efficacy in various inflammatory diseases.     

Anti-inflammatory Effect of Piperine in Adjuvant-Induced Arthritic Rats—a Biochemical Approach

The present study was undertaken to investigate the anti-inflammatory effect of piperine against adjuvant-induced arthritis in rats, an experimental model for rheumatoid arthritis and compared it with that of the non-steroidal anti-inflammatory drug indomethacin. Administration of heat-killed Mycobacterium tuberculosis (0. 1 ml) intradermally into the right hind paw of rats resulted in increased paw volume, lysosomal enzymes, glycoproteins and tissue marker enzymes and decreased body weight. However, these changes were reverted to near normal levels upon piperine (30 mg/kg body weight, i.p.) treatment. Histopathological analysis of joints also revealed that synovial hyperplasia and mononuclear infiltration observed in arthritic rats were alleviated by piperine. Thus, the present study clearly indicated that piperine possesses promising anti-inflammatory effect against adjuvant-induced arthritis by suppressing inflammation and cartilage destruction.     

Effect of antiarthritic drugs on the enhanced interleukin-1 (IL-1) production by macrophages from adjuvant-induced arthritic (AA) rats

The effect of antiarthritic drugs on hindpaw edema and enhanced IL-1 production by macrophages from adjuvant arthritic (AA) rats was determined. Hindpaw edema was inhibited by indomethacin (INDO), methotrexate (MTX) or prednisolone (PRED) but not byd-penicillamine (d-PEN) or chloroquine (CQ). IL-1 production by splenic adherent cells was decreased by MTX and PRED; whereas, IL-1 production by peritoneal exudate cells was decreased by PRED, INDO andd-PEN. This normalization in IL-1 production is not caused by a direct inhibition of IL-1 production by the drugs but most likely reflects clinical improvement in the disease. Whether reduction in IL-1 levels provides a more meaningful parameter than paw edema for assessing clinical efficacy of disease-modifying drugs remains to be determined.Code:L-101     

Time-course of phospholipase A2, eicosanoid release and cellular accumulation in rat immunological air pouch inflammation

Phospholipase A₂ activity in the rat air pouch cavity was determined after induction of a reverse passive Arthus reaction. Time-course of phospholipase A₂ activity appeared to correlate with increased prostaglandin E₂ levels in inflammatory exudate and with the influx of mononuclear inflammatory cells.Local administration of anti-inflammatory drugs such as dexamethasone, indomethacin, or a PLA₂ inhibitor such as p-bromophenacyl bromide significantly inhibited exudate volume, cellular influx, granuloma formation, exudate PGE₂ levels and PLA₂ activity, to varying degrees. Dexamethasone treatment significantly reduced all parameters determined, whereas p-bromophenacyl bromide had a significant inhibitory effect on PLA₂ activity and PGE₂ release, and indomethacin only restored PGE₂ levels.These results show that PLA₂ is neither the only nor the most important factor involved in the development of subchronic inflammation.     

Influence of a diet rich in eicosapentaenoic acid on the development of rat paw oedema and on the formation of prostaglandins I2 and E2

Summary The influence of feeding a marine oil (MaxEPA) with a high content of eicosapentaenoic acid (EPA) to rats for 10 weeks on the development of carrageenin oedema was studied. Since prostaglandins (PGs) are involved in the development of this acute experimental inflammation, the influence of EPA feeding on PG release from aorta (PGI₂) and from the subplantar skin of the inflamed foot (PGI₂, PGE₂) was investigated also. MaxEPA was fed in two daily doses containing 50 or 100 mg EPA/kg/day. In both rat groups there was no influence of EPA on the development of the oedema. However, the capacity of aorta and skin of the plantar region of the experimentally inflamed foot to release PGI₂ was strongly reduced by EPA. On the other hand, the release of PGE₂ from the skin was not reduced. Indomethacin at a low dose (2 mg/kg perorally) reduced the development of the paw oedema as well as the release of PGs in control rats and rats on an EPA-containing diet. It is concluded that EPA did not influence carrageenin oedema because there was an adequate production of the oedema promoting substance PGE₂.     

Alteration of interleukin-1 activity and the acute phase response in adjuvant arthritic rats treated with disease modifying antirheumatic drugs

Interleukin-1 (IL-1) activity and the acute phase response, as measured by plasma CRP and iron, were used to determine if the standard disease modifying antirheumatic drugs (DMARDs), gold, chloroquine andd-penicillamine had a common profile of activity in the adjuvant arthritic (AA) rat. All drugs were tested at a dose which significantly reduced noninjected paw swelling in AA rats. Inhibition of paw edema ranged from 37% ford-penicillamine (100 mg/kg) to 69% for auranofin (10 mg/kg). Two week medication of AA rats with gold sodium thiomalate (GST, 10 mg/kg, i.m.) or auranofin (10 mg/kg, p.o.) resulted in a significant decrease in splenic IL-1 activity, as measured in the standard lymphocyte activating factor (LAF) assay. The acute phase response, often associated with elevated IL-1 activity, was also significantly reduced following treatment of AA rats with 10 mg/kg of GST or auranofin (oral gold). Inhibition of the acute phase response by gold was determined by a significant reduction of plasma CRP levels (56–71% reduction) and enhancement of plasma iron levels (27–52% enhancement).In contrast to the effect of GST and auranofin on IL-1, CRP and iron, treatment with chloroquine (20, 30 and 35 mg/kg) andd-penicillamine (55 and 100 mg/kg) failed to reduce the acute phase response (as measured by plasma CRP and iron) or alter LAF activity from AA rat spleen cell supernatants. Based on its ability to reduce LAF activity in spleen cell supernatants and reduce the acute phase response, it is possible that the activity of gold in the AA rat may in part be due to its ability to inhibit IL-1 productionin vivo. The inability of chloroquine andd-penicillamine to alter LAF activity and the acute phase response in AA rats does not preclude their possession of an immunoregulatory mechanism of action, but it does indicate that their mechanism of action in the AA rat probably differs from that of GST and auranofin.     

The antiphlogistic,antinociceptive and antipyretic properties of fenclorac

Fenclorac (a,m-dichloro-p-cyclohexylphenylacetic acid, diethylammonium salt) is a potent nonsteroidal anti-inflammatory agent with significant analgesic and antipyretic activity. Fenclorac had an ED₅₀ of 7.9 mg/kg in the carrageenan paw edema assay and had a duration of action of 18–22 hours. Comparative tests in the carrageenan paw edema assay in the rat indicated that the potency of fenclorac was 13 times that of aspirin, 3.4 times phenylbutazone, 3 times ibuprofen and 0.3 times indomethacin. Fenclorac was less potent than indomethacin, but more potent than phenylbutazone or aspirin in treatment of developing or established adjuvant arthritis. The anti-inflammatory effectiveness of fenclorac did not depend upon the integrity of the adrenopituitary axis and was not affected by the route of administration or sex of the test animal. Fenclorac was 77 times more potent than aspirin and more than twice as potent as indomethacin in reducing fever in rats rendered hyperthermic with brewer's yeast. Fenclorac did not affect normal body temperatures. Fenclorac did not interfere with cellular immune mechanisms as measured by its lack of effectiveness in experimental allergic encephalomyelitis. Antinociceptive testing indicated that fenclorac had peripheral but not central analgesic activity. Fenclorac had an acute oral LD₅₀ in rats and mice of 285 and 430 mg/kg, respectively. The acute gastric lesion UD₅₀ for fenclorac was 7 mg/kg in the fasted rat. Studies using⁵¹Cr-tagged erythrocytes indicated that fenclorac did not produce significant fecal blood loss in the rat at twice the therapeutic ED₅₀ dose for up to 12 days after dosing. Extensive and prolonged fecal blood loss was observed with a corresponding dose of indomethacin for up to nine days after administration. Comparison of the antiinflammatory pharmacology, Therapeutic Ratio and the data obtained from the⁵¹Cr-fecal blood loss studies indicated that fenclorac was well tolerated after acute or subacute administration to the rat.     

THE β3-ADRENOCEPTOR AGONIST CL316243 PREVENTS INDOMETHACIN-INDUCED JEJUNAL ULCERATION IN THE RAT BY REVERSING EARLY VILLOUS SHORTENING

Jejunal villi undergo early histological shortening and vascular injury in indomethacin-induced ulcerative enteropathy in the rat. The protective effects of the β₃-adrenoceptor agonist CL316243 on this rat model and the mechanism of action were examined using histological techniques. Groups of rats received oral indomethacin (15 mg/kg) and oral CL316243 (0, 0·01–10 mg/kg) 0·5 h beforehand. Jejunal ulceration was assessed 48 h after indomethacin. Other groups received CL316243 either 6 h before or 3 or 6 h after indomethacin. Plasma indomethacin and jejunal prostaglandin E₂ levels were determined in groups of rats with and without prior CL316243. CL316243 was a potent dose-dependent inhibitor of jejunal ulceration (>98 per cent inhibition at doses ≥0·1 mg/kg; ED₅₀=0·025 mg/kg) but was not protective when given 6 h after indomethacin. CL316243, 1 mg/kg, reversed early villous shortening and vascular injury. CL316243 did not affect either indomethacin bioavailability or the inhibition of prostaglandin E₂. To conclude, the β₃-adrenoceptor agonist CL316243 is a potent inhibitor of indomethacin-induced jejunal ulceration and the mechanism of protection involves reversal of both villous shortening and vascular injury, which are usefully assessed by histomorphological techniques.