Mithramycin fluorescence for quantitative determination of deoxyribonucleic acid in single cells

The use of the antibiotic drug mithramycin for cytoflurometric assessment of deoxyribonucleic acid in single cells has been studied in smears of a standard cell population of rat thymocytes. The optimal staining conditions have been determined including the influence of fixation (freeze-drying, formalin and ethanol). The drug equilibration time has been estimated in relation to the concentration of the mithramycin and to Mg++ was found to enhance the fluorescence intensity produced by the mithramycin-deoxyribonucleic acid interaction. The stability and the reproducibility of the fluorescence reaction are discussed.