EFFECTS OF ETHIDIUM BROMIDE ON THE CYTOCHROME CONTENT AND ULTRASTRUCTURE OF L CELL MITOCHONDRIA

Ethidium bromide intercalates between the bases of native DNA, resulting in several biological anomalies. The effects of ethidium bromide on the mitochondria of cultured mouse L cells were studied. At a concentration of 1 µg ethidium bromide/ml it was observed that concentrations of cytochromes a + a₃ and b decreased, a + a₃ more rapidly than b. In contrast, the concentration of cytochromes c₁ and c increased or remained the same as in control cells. Concomitant with the decrease of cytochromes a + a₃ and b was an enlargement of the mitochondria and a reduction in the cristae. The cristae that remained were abnormally organized. After prolonged treatment with ethidium bromide a second population of small, more normally organized mitochondria was apparent. These effects of ethidium bromide could be reversed.