STIMULATED RELEASE OF THE BETA-AMYLOID PROTEIN OF ALZHEIMERS-DISEASE BY NORMAL HUMAN PLATELETS

The circulatory system is a potential source of the beta-amyloid prote in (A beta) of ageing and Alzheimer's disease (AD), platelets accounti ng for the bulk of A beta immunoreactivity detectable in blood. Eviden ce for the release of A beta by platelets, however, has not been repor ted. Platelets from normal donors were therefore stimulated with colla gen to establish if A beta immunoreactive material is released on acti vation. For comparison, the release of the platelet monoamines, seroto nin (5-HT) adrenaline (Adr) and noradrenaline (NA) was also measured. Like the monoamines, collagen-induced) A beta release was concentratio n-dependent, maximal stimulated release exceeding basal efflux by 184% . Collagen EC50 values for A beta release were similar to those for Ad r and NA (3.6 +/- 0.6, 3.4 +/- 0.6 and 3.3 +/- 0.2 mu g/ml collagen, r espectively) but not 5-HT (9.8 +/- 1.9 mu g/ml). These data provide th e first evidence that platelets release AP immunoreactive material on stimulation and may indicate that A beta, Adr and NA reside in the sam e subcellular compartment. (C) 1997 Elsevier Science Ireland Ltd.