8-oxo-deoxyguanosine levels in heart and brain mitochondrial and nuclear DNA of two mammals and three birds in relation to their different rates of aging
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Previous studies found that the rate of mitochondrial oxygen radical generation is lower in long-lived birds than in short-lived mammals. In the present study, the oxidative DNA damage marker 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in heart and brain mitochondrial (mtDNA) and nuclear DNA (nDNA) was compared between mammals and birds of approximately similar body size and metabolic rates; rats (maximum life span, MLSP=4 years) vs pigeons (MLSP=35 years), and mice (MLSP=3.5 years) vs parakeets (MLSP=21 years) or canaries (MLSP=24 years). Lower steady-state 8-oxodG values were observed in all cases in the heart mtDNA in birds than in mammals. 8-oxodG levels were also lower in brain mtDNA in pigeons than in rats, in brain nDNA in canaries than in mice, and in heart nDNA in parakeets compared with mice. The rest of the comparisons did not show significant differences between species. These results taken together indicate that oxidative damage to DNA tends to be lower in birds (highly long-lived species) than in short-lived mammals, specially in the case of mtDNA. This is consistent with the low rate of mitochondrial oxygen radical generation observed in all long-lived species investigated up to date, birds or mammals, including the bird species studied here. The results also show that 8-oxodG steady-state levels are much higher in mtDNA than in nDNA in all the tissues (heart and brain) and species (birds and mammals) studied.
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