Some Effects of Divalent Cations on the Clotting Mechanism and the Platelets of EDTA Blood

Abstract

Metal EDTA chelates, the stability constant of which is higher than that of calcium, fail to act as anticoagulants, whereas magnesium and barium EDTA prevent clotting. SrEDTA is not an effective anticoagulant. Blood prevented from clotting by magnesium or barium EDTA, or by half the usual quantity of disodium EDTA, fails to show certain peculiar characteristics seen in disodium EDTA blood. These characteristics are: long thrombin clotting time, rapid Ac globulin (factor V) destruction, absence of clot retraction, spherical shaped platelets and diminished platelet adhesiveness to glass and agglutinability. Addition of MgCl₂, BaCl₂, SrCl₂ or CaCl₂ to disodium EDTA blood corrects the thrombin clotting time and clot retraction and diminishes Ac-globulin destruction. MgCl₂ changes the spherical platelets to discs and increases platelet adhesiveness. The concentration of divalent cations required to correct the behavior of disodium EDTA blood is much less than the concentration of calcium or strontium required to produce even trace fibrin formation. It is suggested that magnesium may normally be responsible for maintaining a short thrombin clotting time, platelet disc shape and adhesiveness and for slowing Ac-globulin destruction. Submitted on January 14, 1958