Binding of platelet-activating factor to platelets of Alzheimer's disease and multiinfarct dementia patients.

The binding of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor, PAF) to platelets was studied in 22 patients with probable Alzheimer's disease (AD), 11 with multi-infarct dementia (MID), 22 age-matched normal old controls, and 20 young subjects. The results showed a significantly lower degree of PAF binding to platelets of AD and MID patients than in those of the old controls and young subjects (133.3 +/- 8.5, and 123.4 +/- 16.5 vs. 202.3 +/- 11.6 and 206.7 +/- 17.3 receptors/cell, respectively; p < 0.01). These differences were due to reduced Bmax, while Kd remained unchanged. No significant difference was observed between the PAF binding to platelets of AD and MID patients nor between that of old and young controls. No correlation was found between age and binding in the various elderly groups. However, a significant correlation was found between PAF binding and degree of cognitive impairment in the AD patients. This is the first evidence to support a possible involvement of PAF in dementing disorders.