Differences in the Redox Balance in Human Rheumatoid and Non-rheumatoid Synovial Lining Cells

Abstract

Summary Human rheumatoid and non-rheumatoid synovial lining cells have been studied by scanning and integrating microdensitometry. The ferric ferrocyanide reaction, controlled by blockade with mercury or maleimide, has been used for investigating sulphydryl groups; glucose 6-phosphate dehydrogenase and NADPH-diaphorase activities have been studied by quantitative tetrazolium cytochemistry. It has been shown that a greater proportion of sulphur-containing proteins in the rheumatoid cells are in the reduced (sulphydryl) state than in the non-rheumatoid cells. This supports the suggestion that the redox balance of human rheumatoid synovial lining cells is displaced towards the more reductive condition. Further support is given by the finding that, in the rheumatoid cells, the rate of production of NADPH-hydrogen by glucose-6-phosphate dehydrogenase activity is about 4 times greater than in the equivalent non-rheumatoid cells; there is little change in the rate of oxidation of the reduced NADP, so indicating the possibility of a metabolic basis to the reductive imbalance in the rheumatoid cells.