Phosphate Groups (Receptors ?) on the Surface of Human Blood Platelets

PLATELET adhesion and aggregation, which are believed to depend on the surface charge, play a central part in haemostasis and thrombosis 1 . Human blood platelets at physiological p H in saline or plasma exhibit a net negative charge 2–4 . α-Carboxyl groups ( pK 2·8) of neuraminidase susceptible N-acetylneuraminic acid (NANA) contribute about 43 per cent of the electron charges 3,5–7 . Platelet aggregation and stickiness are commonly observed when these negative charges are blocked 8–10 or eliminated 11 by enzyme treatment, marked agglutination being observed in the isoelectric range (approximately 4) (ref. 2). Artificial materials (dextran and plastics) are being used extensively in medicine and surgery. The mechanism of the interaction of platelets with “foreign” surfaces and endothelial wall in vascular injury, leading to the release of platelet constituents 12–14 and the consequent plug formation is of considerable clinical interest. To suppress pathological thrombosis, it may be necessary to develop suitable chemical agents capable of interfering with one or several of the reaction steps involved in the aggregation of platelets. Numerous chemicals are under study 15 .