This study was performed to elaborate the best conditions for measuring the redox activity of Ehrlich
ascites tumour cells by using a new
tetrazolium salt, cyantolyl tetrazolium
chloride (CTC). This
tetrazolium salt forms a fluorescent water-insoluble
formazan on reduction on the surface of intact vital cells. The influences of fixation and of various substrates and electron carriers on the cellular reduction of CTC were investigated quantitatively using an elution technique. The amount of
formazan obtained after incubating vital cells with
Meldola Blue as electron carrier was greater than that obtained with
Methylene Blue,
menadione,
2,6-dichloroindophenol,
1-methoxyphenazine methosulphate or
phenazine methosulphate. Using flow cytometry, the
formazan production per cell and, after staining the nuclear
DNA, the distribution of the redox activity in the cell population can be visualized with satisfactory resolution. We conclude from our findings that
dehydrogenases are only partially involved in the reduction of
tetrazolium salts by intact cells and that a redox activity, probably related to a cell membrane-bound
NAD(P)H-oxidase system, is mainly measured.