No effect of treatment with carcinogens on cytosine methylation of mitochondrial DNA isolated from rat organs by phenol-free alkaline extraction

Due to the postulated role of mitochondrial DNA damage in aging as well as in the pathogenesis of several chronic degenerative diseases, including tumors, there is a need for easy, safe, rapid and inexpensive methods for mitochondrial DNA isolation. We propose a simple, 1-day protocol based on alkaline extraction, which avoids time-consuming gradient centrifugations and use of toxic phenol. This procedure was used for the recovery of mitochondrial DNA from different rat organs (liver, kidney, heart, lung, brain and testis). The yield was quite high. Purity was sufficient enough to perform restriction analyses with several endonucleases. No changes were observed in the structure or methylation patterns of -CCGG- sites in liver mitochondrial DNA isolated from rats exposed whole-body to mainstream cigarette smoke or treated with the carcinogens benzo[a]pyrene, 2-acetylaminofluorene or diethylnitrosamine.