Differences in ethidium bromide and 4 '-6-diamidino-2-phenylindole staining profiles with regard to DNA fragmentation during apoptosis

To simply and directly evaluate DNA fragmentation during apoptosis induced in mouse cultured hepatocytes by an anti-Fas antibody, we examined the fluo rescence intensity in cell nuclei stained with ethidium bromide and 4'-6-di amidino-2-phenylindole by optiphoto fluorescence microscopy. The intensity of the former staining for the nuclear DNA of apoptotic cells was clearly d ecreased compared to that of non-apoptotic cells, whereas no difference in the fluorescence intensity for the latter stain between the apoptotic and n on-apoptotic groups was observed. Thus, the use of optiphoto fluorescence m icroscopy, in conjunction with both stains, constitutes a useful tool for t he evaluation of apoptotic DNA fragmentation.