REPAIR OF OXIDATIVE DAMAGE WITHIN THE MITOCHONDRIAL-DNA OF RINR-38 CELLS

A growing body of evidence suggests that a variety of chronic diseases , including cancer and diabetes, are associated with damage to mitocho ndrial DNA. Since mitochondria are constantly exposed to high levels o f reactive oxygen species, it is likely that oxidative damage to mitoc hondrial DNA may be responsible for some of these maladies. To determi ne whether mitochondria can repair this damage, a quantitative Souther n blot technique was utilized to identify repair in specific DNA fragm ents. A 10.8-kilobase mitochondrial restriction fragment was studied e mploying a probe containing the entire mouse mitochondrial genome. All oxan was employed to generate oxygen radicals. Insulinoma cells were e xposed to alloxan for 1 h, and total cellular DNA was isolated immedia tely or after intervals of up to 8 h. Alkali treatment was used to ide ntify abasic sites and sugar lesions, endonuclease III was used to ide ntify lesions associated with thymine and cytosine damage, and formami dopyrimidine-DNA glycosylase was employed to recognize formamidopyrimi dines and 8-oxoguanines in DNA. The results showed that all forms of d amage studied were repaired by 4 h, indicating that mitochondria are a ble to efficiently repair damage to their DNA caused by reactive oxyge n species.