Electrophoretic separation of alkaline phosphatase isoenzymes in synovial fluid and serum from patients with rheumatoid arthritis.

The alkaline phosphatase enzyme in both serum and synovial fluid from 28 cases of rheumatoid arthritis and from the serum of 30 controls was measured. The enzyme was further studied by separating its isoenzymes to clarify their origin in both synovial fluid and serum of 10 patients with elevated level of the enzyme in their sera. The level of the enzyme in serum was elevated in 37% of patients confirming previous reports on that point. The most abundant isoenzyme in the synovial fluid (66.9%) was found to be bone in origin while in serum the most abundant isoenzyme was found to be hepatic (60.5%). This may be responsible for increased bone turn-over in rheumatoid joints whether in formation or resorption.