Copper-zinc superoxide dismutase activity in red blood cells in probable Alzheimer's patients and their first-degree relatives.

The activity of the enzyme copper-zinc superoxide dismutase (Cu-Zn SOD) has been investigated in red blood cell (RBC) homogenate obtained from demented patients with probable Alzheimer's disease (DAT), from their first-degree relatives (sisters/brothers and sons/daughters), and from healthy control families of the same age. A statistically significant increase in SOD activity (P < 0.01) was found in RBC's homogenate between families of DAT patients (not including the demented individual) and control families. Variability in SOD activity due to differences between families was not significant for DAT relatives; a significant variance component (P < 0.05) was found between control families. Additionally, a statistically significant increase in SOD activity (P < 0.001) with age in DAT patients up to 70 years and a significant decrease above this age were found, confirming a previously found relation. No changes in SOD activity with age were detected in healthy controls nor in DAT relatives. The increased levels of Cu-Zn SOD, probably represent a general alteration of the oxidative processes characteristic of this dementia and support the proposal that the enzyme could be used as an early diagnostic peripheral marker of the Alzheimer's disease (AD), and to determine to which subgroup the patient belongs, as well as a risk factor in non-demented first-degree relatives.