The sensitivity to light of solutions of phenazine methosulphate: a quantitative cytochemical study.

The ability of phenazine methosulphate to transfer electrons from reduced coenzymes to a tetrazolium salt, neotetrazolium chloride, after exposure to light for various periods of time has been studied. Enzymes assayed for this purpose were: glucose-6-phosphate dehydrogenase been studied. Enzymes assayed for this purpose were: glucose-6-phosphate dehydrogenase (NADP+-dependent); lactate dehydrogenase (NAD+-dependent) and succinate dehydrogenase (flavoprotein-dependent). Enzyme activity was measured in sections of rodent liver by scanning and integrating microdensitometry. Phenazine methosulphate in solution was found to be sufficiently stable in light for up to two hours for reproducible quantitative measurements of cytochemical dehydrogenase activity to be obtained over this period.