A tissue kallikrein in the synovial fluid of patients with rheumatoid arthritis

Tissue kallikrein is an enzyme that forms the vasoactive peptide
kallidin from an endogenous substrate L-kininogen. Tissue
kallikrein has been identified in joint fluids and in inflammatory
infiltrates within synovial membranes. It is suggested that tissue
kallikrein and kinins have an important role in synovitis and joint
damage. Immunoreactive tissue kallikrein and amidase activity were
both measured in the synovial fluid of 24 patients with rheumatoid
arthritis (RA) and 12 with osteoarthritis (OA). Active enzyme
concentrations were higher in RA than in OA and correlated well
with the lysosomal enzymes beta-glucuronidase and lactate
dehydrogenase. Both total immunoreactive tissue kallikrein and the
proenzyme values were similar in RA and OA. Tissue kallikrein was
localised by immunocytochemistry to the polymorphonuclear
leucocytes present in the synovial fluid and membranes of patients
with RA.