Decreased DNA repair capacity in familial, but not in sporadic Alzheimer's disease.

Using the alkaline filter elution technique we determined the induction and disappearance of DNA single-strand breaks (SSB) in freshly isolated peripheral blood lymphocytes (PBL) from 43 Alzheimer's disease (AD) patients and 48 normal, healthy age- and sex-matched control subjects following in vitro exposure to N-ethyl-N-nitrosourea (ENU). The mean percentage SSB disappearance in PBL from control subjects at 1 h after ENU treatment was 41.4 +/- 2.9%; this was not significantly different from that found in samples from AD patients which had no (n = 16) or one (n = 12) first-degree relative with dementia (42.5 +/- 8.2% and 43.0 +/- 4.4%, respectively; p greater than 0.75). However, in PBL of 15 AD patients with at least two first-degree relatives with dementia the mean percentage SSB disappearance was 23.6 +/- 5.8%, which was significantly lower than that found in controls (p less than 0.01) or in the other AD patients (p less than 0.02).