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 fluorescence intensity in cell nuclei stained with ethidium bromide and 4'-6-diamidino-2-phenylindole by optiphoto fluorescence microscopy. The intensity of the former staining for the nuclear DNA of apoptotic cells was clearly decreased compared to that of non-apoptotic cells, whereas no difference in the fluorescence intensity for the latter stain between the apoptotic and non-apoptotic groups was observed. Thus, the use of optiphoto fluorescence microscopy, in conjunction with both stains, constitutes a useful tool for the evaluation of apoptotic DNA fragmentation.