Platelet of Alzheimer patients: increased counts and subnormal uptake and accumulation of [14C]5-hydroxytryptamine.

Platelets are the main source of 5-hydroxytryptamine (5-HT) and amyloid precursor protein (APP) found in plasma. We studied a possible correlation between platelet markers and the clinical diagnosis of Alzheimer disease (AD). Our results indicate that in AD patients: (a) platelets are elevated, (b) their ability to accumulate 5-HT decreases and, (c) the kinetic parameters of 5-HT uptake are altered (decreased Km and Vmax), compared to non-demented healthy individuals. An aged Down syndrome patient presents even more deviant alterations. Our findings supports the idea that platelets may provide a systemic marker of AD, and eventually be useful for the clinical diagnosis of the disease.