The Journal of clinical investigation
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Dilute whole blood clots were prepared by addition of thrombin to blood diluted 1:10 in phosphate buffer. The pH of this buffer was 7.4 and the ionic strength was 0.084. Though the ionic strength was low, there was no hemolysis of red corpuscles due to the contribution to the osmotic gradient by plasma salts and proteins. ⋯ Reconstitution of inactivated serum with purified C4, 3, and 5 and thrombin restored its capacity to induce aggregation and retraction of platelets. Therefore, we postulated that platelet aggregation and retraction were necessary for clot retraction and that platelet aggregation and clot retraction facilitated clot lysis. More specifically we postulated that thrombin, in addition to catalyzing clot formation, also modified the platelet membrane such that gammaM globulin (cold agglutinin) and complement components can act on the platelet membrane leading to (a) aggregation and retraction of the platelets, (b) retraction of the clot, and (c) to the activation of plasminogen either on the surface of the platelet by C8i and (or) by release of platelet activators of plasminogen.