title: Conditions influencing the interaction of asialo von Willebrand factor with human platelets--the effects of external ionized calcium concentration and the role of arachidonate pathway.
abstract: We have studied the interaction of ASvWf with human platelets in PRP and in suspensions of washed platelets containing either physiological or low external ionized calcium concentration [Ca2+]o. In hirudin-PRP or in washed platelets in 1.5-2 mM CaCl2, ASvWf up to 50 micrograms/ml does not induce platelet aggregation or the release reaction. When [Ca2+]o is decreased by addition of citrate to hirudin-PRP or when no CaCl2 is added to washed platelet suspensions, ASvWf does induce platelet aggregation and the release reaction. In low [Ca2+]o, ASvWf interacts with platelet GPIb to cause primary aggregation of disc-shaped platelets to each other through GPIIb/IIIa, with or without added fibrinogen. This primary platelet aggregation leads to thromboxane A2 formation and secondary aggregation and the release reaction. With [Ca2+]o in the physiological range, there is less ASvWf interaction with GPIb, no primary platelet aggregation and no thromboxane A2 formation. The ASvWf-platelet interaction at physiological [Ca2+]o, however, enhances the platelet response to collagen or epinephrine.
authors.affiliation: A. Bianchi Bonomi Hemophilia and Thrombosis Centre, University of Milano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Cattaneo
authors.forename: J F
authors.initials: JF
authors.lastname: Mustard
authors.forename: M T
authors.initials: MT
authors.lastname: Canciani
authors.forename: M
authors.initials: M
authors.lastname: Richardson
authors.forename: A B
authors.initials: AB
authors.lastname: Federici
authors.forename: P M
authors.initials: PM
authors.lastname: Mannucci
mesh_terms: D001095:Arachidonic Acids / Q000502:physiology*; D001212:Asialoglycoproteins; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000032:analysis / Q000494:pharmacology*; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D013929:Thromboxane B2 / Q000096:biosynthesis; D014841:von Willebrand Factor / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D001212:Asialoglycoproteins; D010975:Platelet Aggregation Inhibitors; C044131:asialo-von Willebrand Factor; D014841:von Willebrand Factor; D013929:Thromboxane B2; D006493:Heparin; D004492:Edetic Acid; D002118:Calcium