The activities of four enzymes …… lactic dehydrogenase (LDH) with its isozymes, beta-glucuronidase (beta-G) with its isozymes, acid and alkaline phosphatases, were studied in serum, synovial fluid and synovial membrane obtained from 45 patients with rheumatoid arthritis (RA) and 17 patients with osteoarthritis (OA). The control group comprised sera from 20 normal subjects, synovial fluid and membrane from 10 patients who had no clinical evidence of joint disease prior to death and leukocytes isolated from normal human peripheral blood. The LDH isozyme was identified five fractions by means of agar gel electrophoresis, and the beta-G isozyme was shown to be composed of three fractions by the method using DEAE
Sephadex A-50 column chromatography: beta-G Ⅰ activity in serum has been localized in gam maglobulin, beta-G Ⅱ in beta-globulin, and beta-G Ⅲ in alpha 1, alpha 2-globulin and albumin regions. In the present study, the author obtained the results as follows. 1) The activities of LDH, beta-G and acid phosphatase in synovial fluid from RA patients were extremely increased and significantly higher than from OA patients or cadavers, but alkaline phosphatase activity remained in low level. 2) The total LDH activity in rheumatoid synovial fluid was 1640u/ml, and 473u/ml in rheumatoid serum (P<0.001) Their isozyme patterns demonstrated qualitatively increased amounts of LDH-5 (35.7%) in rheumatoid synovial fluid and LDH-1 (39.2%), LDH-2 (36.7%) in rheumatoid serum. 3) The activities of LDH, beta-G, acid and alkaline phosphatases in synovial fluid from OA patients were not increased (approximately to the values of normal human serum), but its LDH-5 (22.5%) was minimally elevated. 4) Rheumatoid synovial membrane also revealed a significantly higher LDH-5 activity (39.3%) than in cadavers (14.6%). 5) The isozyme of leukocytes was found to be characterized by increased amounts of LDH-3 (43.7%) and no increase of LDH-5 (5.1%). 6) In regard to beta-G isozymes, only beta-G Ⅲ activity was significantly elevated in rheumatoid synovial fluid (50.6%) and rheumatoid synovial membrane (57.7%). 7) The beta-G isozyme of leukocytes comprised large amouts of beta-G Ⅱ, and beta-G Ⅲ was prominant in synovial membrane of cadavers. 8) These results suggest that raised enzyme activities in rheumatoid synovial fluid have been derived mainly from inflamed synovial membrane rather than from synovial leukocytes.