Characterization of platelet binding of heparins and other glycosaminoglycans.
The binding of glycosaminoglycans to intact washed human platelets was studied. The platelet binding of a 3H-labeled unfractionated heparin was saturable and reached equilibrium in 10-15 minutes. Heparin binding was specific: a 50-fold molar excess of an equivalent unlabeled heparin displaced up to 90% of labeled heparin, while chondroitin sulfate A and hyaluronic acid minimally displaced the binding of labeled heparin. Low molecular weight heparin fragments showed intermediate efficacy in displacing the binding of unfractionated [3H]heparin. Dextran sulfate (Mr 8,000, sulfation 17%) was as potent as unfractionated heparin in displacing binding, while neutral dextrans were ineffective. We observed that platelet activation by the calcium ionophore A23187 increased heparin binding by 2 to 3-fold, principally by enhancement of binding capacity not binding affinity. This process of heparin binding to the platelet surface may mediate some of the reported effects of heparin on platelet behavior.
D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D006025:Glycosaminoglycans / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism*; D006801:Humans
D006025:Glycosaminoglycans; D000001:Calcimycin; D006493:Heparin