O6-methylguanine-DNA methyltransferase in lymphocytes of the elderly with and without Alzheimer's disease.
Deficiency in DNA repair has been linked to aging, mutagenesis, carcinogenesis and several types of primary neuronal degeneration. O6-Methylguanine-DNA methyltransferase is a key enzyme in the repair of DNA alkylation damage that removes a methyl group from the O6 position of methylguanine. This study was carried out to determine whether there were any changes in the activity of this enzyme in lymphocytes of patients with Alzheimer's disease (AD) as compared to lymphocytes of age-matched non-demented elderly. The transferase activity in lymphocytes from 19 elderly patients with AD (mean 87.7 fmole/100 micrograms protein +/- SD 44.7) was not statistically different from that in 19 age/sex-matched controls (mean 91.3 fmole/100 micrograms protein +/- SD 40.0). There was no significant trend with age in transferase activity and the activity levels in the elderly subjects studied were the same as those reported previously for younger individuals by this laboratory. It is concluded that a reduction in O6-methylguanine-DNA methyltransferase activity is unlikely to be involved in the etiology or the pathogenesis of AD.