An improved technique for the assay of red blood cell superoxide dismutase (SOD) activity.

Superoxide dismutase (SOD) activity of erythrocytes from normal pregnant women (controls) and from pre-eclamptic toxaemia (PET) cases was determined by the method of Winterbourn et al. (J Lab Clin Med 1975;85:337-341) with slight modifications. Instead of the Michaelis-Menten type of plot that is usually obtained and which these authors have found to be imprecise, a linear plot was obtained when the reciprocal values for the percentage inhibition of nitroblue tetrazolium (NBT) reduction were plotted against the corresponding volumes of red blood cell (RBC) extract. This plot was found to give precise values for the volumes of RBC extracts required for 50% inhibition of NBT reduction. Consequently, a clearer understanding is beginning to emerge regarding the SOD activity of PET cases compared with that of normal pregnant women.