Alkylation damage and repair in Alzheimer's disease lymphocytes.

We have previously shown that lymphocytes from Alzheimer's disease (AD) patients are hypersensitive to ionising radiation, as revealed by their higher levels of dicentrics than those from age-matched, normal individuals. We have now examined the sensitivity of these cells to N-methyl-N-nitrosourea or methyl methanesulphonate, using a variety of assays, namely unscheduled DNA synthesis, viability, sister chromatid exchange and, via high performance liquid chromatography, level of methylation and repair of the adducts, 7-methylguanine, 0(6)-methylguanine and 3-methyladenine. We have found that AD lymphocytes and age-matched normal lymphocytes respond similarly to methylation damage, as assessed by all these techniques.