Marked elevation of serum N-acetyl-beta-D-hexosaminidase activity in rheumatoid rheumatoid arthritis

Objective. To study N-acetyl-beta-D-hexosaminidase (NAHase) activity in the sera of rheumatoid arthritis (RA) patients and to determine its source. Methods. NAHase activity in the serum and synovial fluid of RA patients was measured with p-nitrophenyl beta-N-acetylglucosaminide as substrate. The p -nitrophenol released was measured spectrophotometrically in an ELISA reade r. Rabbit articular chondrocytes in primary culture were stimulated with in terleukin-1 beta (IL-IP). Results. Serum NAHase activity was higher in 35% of the RA patients than in healthy patients. The median activity was about twice that of the serum of healthy, volunteers. RA patients with high serum NAHase activity also had more joint destruction (85%) than those with normal NAHase activity (57%, p < 0.05), but their inflammatory status was similar The source of NAHase in RA was investigated by assaying it in RA synovial fluids (SF) and measurin g its release fi-om articular chondrocytes in primary culture. NAHase activ ity was detected in all 23 RA SF; at a median concentration that was 2 time s that of the serum. NAHase activity ill the medium of articular chondrocyt es was stimulated by IL-IP (p < 0.005 compared to unstimulated cells), sugg esting that cartilage is a source of serum and SF NAHase activity. Conclusion. The serum concentration of the matrix hydrolase, NAHase, is hig her in destructive RA than in inflammatory RA.