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 microg ethidium bromide/ml it was observed that concentrations of cytochromes a + a(3) and b decreased, a + a(3) more rapidly than b. In contrast, the concentration of cytochromes c(1) and c increased or remained the same as in control cells. Concomitant with the decrease of cytochromes a + a(3) 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.