Tissue-specific susceptibility to peroxyl radical-mediated inhibition of mitochondrial transcription.

Proper mitochondrial function requires the continual maintenance of the integrity of the mitochondrial gene expression system. We have recently shown, using rat liver mitochondria, that the mitochondrial transcription system is extremely sensitive to inhibition by peroxyl radicals. In this report, we demonstrate that the transcription process in mitochondria isolated from rat heart and brain are more resistant to this oxidative insult than is the transcription machinery in liver mitochondria. This finding is in contrast to the generally observed trend that liver and liver mitochondria are equally or better protected against oxidative stress, and highlights the differential oxidant-specific anti-radical defenses in mitochondria isolated from these tissues. Finally, in conjunction with previous data, these results demonstrate the existence of a potent, tissue-specific anti-radical resistance capacity that protects the mitochondrial gene expression system.