REDUCED PHOSPHATIDYLINOSITOL KINASE-ACTIVITY IN ALZHEIMERS-DISEASE - EFFECTS OF AGE AND ONSET

Phosphatidylinositol kinase (PI kinase) and phosphatidylinositol phosp hate kinase (PIP kinase) were assayed in a membrane-free cytosolic fra ction prepared from the medial temporal cortex of patients with Alzhei mer's disease (AD) and nondemented controls, with exogenous lipids as substrate. P-32-PIP formation appeared to be reduced by 21 % in patien ts with AD who died before 80 years, compared to matched controls. In addition, there was an age-related decrease in PI kinase activity in t he control group. In the AD patients there was no age-related decrease . Very old AD patients (older than 80 when they died) with a short dur ation of the disease were characterized by increased PI kinase activit y. No differences were found in the closely related enzyme PIP kinase. The results are indicative for heterogeneity in AD.