Effect of 6-Methoxy-2-Naphthylacetic Acid (6MNA), the Active Metabolite of Nabumetone, on the Glycosaminoglycan Synthesis of Canine Articular Cartilage In Vitro

6-methoxy-2-naphthylacetic acid (6MNA), the active metabolite of nabumetone, a novel nonacidic NSAID, has been studied in an in vitro culture system to determine its effects on glycosaminoglycan synthesis of normal and osteoarthritic canine articular cartilage. The effects were contrasted with those of several other NSAIDs. Dexamethasone potently inhibited synthesis and was used as a positive control in these studies. To reduce the influence of protein binding with these drugs, experiments were performed both in the presence and in the absence of serum in the culture medium. At and above concentrations achieved in the plasma of nabumetone-treated patients, 6MNA did not inhibit glycosaminoglycan synthesis of normal or osteoarthritic cartilage. In contrast, some other NSAIDs had the propensity to significantly suppress chondrocyte synthetic activity.