4 THE EFFECTS OF EXERCISE AND INJURY ON CHONDROITIN SULFATE AND KERATAN SULFATE CONTENT IN EQUINE SYNOVIAL FLUID.

Our previous work, as well as that of others, has shown that injury-mediated activation of cartilage matrix degradation in adult horses results in proteolytic fragmentation of aggrecan, which in turn results in the release of chondroitin sulfate (CS) and keratan sulfate (KS) substituted degradation fragments into the synovial fluid and serum. We hypothesized that measurement of these degradation products by fluorophore-assisted carbohydrate electrophoresis (FACE) may provide useful markers of acute joint injury. Methods: By using FACE, CS and KS content were measured in equine carpal synovial fluid. Specifically, chondroitinase ABC/ACII products non-sulfated chondroitin (∆di0S), chondroitin-6-sulfate (∆di6S), and chondroitin-4-S (∆di4S) were quantitated. Additionally, the keratanase II/ endo-β-galactosidase products of KS the monoand disulfated disaccharides, galβ1,4glcNAc6S (monoS) and gal6Sβ1,4glcNAc6S (diS) were measured. Four groups of horses were compared: (1) racehorses undergoing arthroscopic surgery, (2) age-matched horses with chronic osteoarthritis (OA), (3) age-matched, normal unexercised controls, (4) treadmill trained horses, both before and after stress testing. The stress test was a period of maximal exercise in which treadmill speed was incrementally increased until the horse could no longer maintain position on the treadmill. The protocol was approved by the Institutional Animal Care and Use Committee. Results: Significant differences were observed between groups for a number of the GAG disaccharides, most notably ?diOS, ?di4S, and DiS (Table 1). ?diOS and ?di4S concentrations are plotted in Fig 1.