ANTIINFLAMMATORY EFFECTS OF TOPICALLY APPLIED DIMETHYL-SULFOXIDE GEL ON ENDOTOXIN-INDUCED SYNOVITIS IN HORSES

Objective-To evaluate the effect of topically applied dimethylsulfoxid e (DMSO) on lipopolysaccharide (LPS)-induced synovitis in the mid-carp al joint. Animals-6 sound, healthy, adult horses (12 carpi). Procedure -In a double-blinded, crossover, paired study with a 1-week washout pe riod, mid-carpal joints were allocated to group 1 (DMSO, n = 6) or gro up 2 (control, n = 6). Each joint was injected with 1.3 mi (0.0125 ng/ dl) of LPS to induce synovitis. For group-1 joints, DMSO gel (15 g; 90 %) was applied after injection of LPS and at 12-hour intervals for 60 hours. Joints of group 2 received LPS, but not DMSO gel. All horses we re evaluated by serial lameness examinations and synovial fluid analys es (total and differential WBC count and total protein concentration) at 12-hour intervals for 60 hours after LPS injection. Plasma and syno vial fluid were obtained at baseline and 36 hours to document presence of DMSO. Results-Mean WBC concentration was significantly (P < 0.05) lower in group-1, compared with group-2 joints,;at 24 hours and had a trend to be lower at 36 hours. Mean total neutrophil count was signifi cantly lower in group-1, compared with group-2 joints at 24 hours. In group-1 joints, DMSO was detected by use of gas chromatography in the synovial fluid of 5 of 6 joints and in plasma from 1 of 6 horses. Conc lusion-Topically applied DMSO penetrated into synovial fluid in suffic ient quantities to be detected and to decrease joint inflammation.