PHOSPHOINOSITIDE KINASE-ACTIVITIES IN SYNAPTOSOMES PREPARED FROM BRAINS OF PATIENTS WITH ALZHEIMERS-DISEASE AND CONTROLS

Previously phosphatidylinositol (PI) kinase activity in cytosolic frac tions prepared from postmortem tissue of the cerebral cortex from pati ents with Alzheimer's disease (AD) appeared to be lower than that of a ge-matched controls [Jolles et al., J. Neurochem., 58 (1992) 2326-2329 ]. In the study presented here, PI and PIP (phosphatidylinositol phosp hate) kinase activities were studied in synaptosomes prepared from pos tmortem brain tissue of AD patients and age-matched controls. Firstly, PI kinase activity in synaptosomes prepared from the frontal superior gyrus of AD brain was 30% lower than in synaptosomes prepared from po stmortem tissue of control brain. PIP kinase activity was the same in AD and control synaptosomes. Secondly, the yield of synaptosomal prote in (mu g protein per mg tissue wet weight) was lower in preparations f rom AD brain than in preparations from control brain, which could be a manifestation of a loss of presynaptic terminals in the frontal corte x. These results suggest that the difference in PI kinase activity bet ween AD and control brain tissue may originate from differences in int act neurons in view of the fact that synaptosomes can originate only f rom intact neurons.