The effect of detergents on the reduction of tetrazolium salts

Detergents, such as Triton X-100, markedly increase the reduction of tetrazolium salts by xanthine oxidase plus xanthine, or by NADH. This effect of detergent, in the case of the xanthine oxidase catalyzed process, is seen aerobically but not anaerobically. Increasing the rate of accumulation of formazan, whether by increasing the concentration of the tetrazolium salt or by adding detergent, decreased susceptibility to inhibition by superoxide dismutase or by O2. These results are accommodated by a scheme of reactions the essence of which is the univalent reduction of the tetrazolium to an uncharged tetrazoinyl radical which can reduce O2 to O2- or which can partition into the detergent micelles and there dismute to generate the stable formazan.