Measurement of oxidatively induced base lesions in liver from Wistar rats of different ages

Mitochondrial and nuclear DNA were isolated from the livers of young (6-7 m onth) and old (23-24 month) Wistar rats and the levels of 10 different oxid atively induced lesions were analyzed by gas chromatography/mass spectromet ry. This is the first study to measure several different oxidatively induce d base lesions in both mitochondrial and nuclear DNA as a function of age. No significant age effects were observed for any lesion. Furthermore, contr ary to expectations, we did not observe elevated levels of oxidatively indu ced base lesions in mitochondrial DNA. This contrasts with 50-fold differen ces reported for several lesions between mitochondrial and nuclear DNA from porcine liver (Zastawny et al., Free Radic. Biol. Med. 24:722-725, 1998). The fact that different lesion levels are observed even when similar techni ques are employed emphasizes that the role of oxidative mitochondrial DNA d amage and its repair in aging must continue to be the subject of intense in vestigation. Questions concerning endogenous levels of damage should be rev isited as existing methods are improved and new methods become available. ( C) 1999 Elsevier Science Inc.