The Antioxidant Proteins of Extracellular Fluids *

Primitive obligate anaerobes of the oxygen-free period had to either avoid or evolve to live with the high levels of solar radiation. Aerobic life processes utilize molecular oxygen for the controlled oxidation of carbon-containing molecules with the concomitant release of energy and the reduction of oxygen to water. Some samples of synovial fluid from rheumatoid patients show bleomycin-detectable iron in amounts correlated to disease severity. The serum of some patients with rheumatoid arthritis contains raised concentrations of ceruloplasmin, and this confers a greater ferroxidase-dependent antioxidant activity on the fluid. Serum and synovial fluid taken from patients with active rheumatoid arthritis tend to have lower antioxidant activities, compared to controls, when tested for their ability to inhibit copper-promoted lipid peroxidation. The antioxidant defenses of extracellular fluids appear to be primarily directed towards containing the reactivity of metal ions in the presence of reduced oxygen intermediates, rather than directly removing the oxygen intermediates themselves.