The relationship between erythrocyte superoxide dismutase activity and erythrocyte copper levels in normal subjects and in patients with rheumatoid arthritis.

A quantitative assay for erythrocyte superoxide dismutase activity using the xanthine-xanthine oxidase-nitro blue tetrazolium system which is applicable to clinical material is described. The in-batch precision of the method is 3.5% and the between-batch precision is 8.8%. Employing this assay, erthrocyte superoxide dismutase activities were measured in 50 normal subjects and in 50 patients with rheumatoid arthritis. There was no significant correlatiion between superoxide dismutase activity and erthrocyte copper concentration. Erythrocyte copper was lower in female rheumatoid patients than in normals. This difference was not accompanied by a difference in superoxide dismutase activity.