Quantitative Aspects of Antithrombin and Heparin in Plasma
- 29 February 1956
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Legacy Content
- Vol. 184 (3) , 627-639
- https://doi.org/10.1152/ajplegacy.1956.184.3.627
Abstract
An examination is made of the characteristics of antithrombin and heparin in plasma as described in the literature. Antithrombin action follows the equation - dT/dt = k1T(A0 – T0 + T – k2t) + k2 where T, A and t refer to thrombin, antithrombin and time in minutes, respectively. One unit of antithrombin is considered to inactivate one NIH unit of thrombin. Subscripts refer to initial concentrations. The rate constant k1, = 0.0066 ± 0.0007 refers to an apparent bimolecular reaction between thrombin and antithrombin and the rate constant k2 = 0.008 ± 0.0014 to an apparent zero order thrombin decay. A comparison of the effect observed when heparin is added to plasma with those obtained on an isolated heparin cofactor preparation ( Arch. Biochem. & Biophys. 58: 431, 1955) suggests that an independent heparin cofactor does not exist in normal plasma. The action of heparin in plasma may be accounted for quantitatively by two effects. First, an increase by a factor of approximately 20 in the rate at which antithrombin inactivates thrombin and second, a decrease in the capacity of antithrombin to inactivate thrombin by a factor of 1.9 or 2.2, depending on whether or not a small (15%) portion of the antithrombin normally present is insensitive to heparin. It is suggested that isolated ‘heparin cofactors’ originate from normal antithrombin. Saline dilution of plasma produces a profound change in antithrombin capacity as well as in rate of thrombin inactivation. The minimum capacity (35% of normal when referred to 1 ml original plasma) occurs at a 3-fold plasma dilution, about 90% of the original capacity reappearing when a 20-fold dilution is used.Keywords
This publication has 12 references indexed in Scilit:
- The antithrombin activity of human plasmaBiochemical Journal, 1954
- The antithrombin activity of heparinBiochemical Journal, 1954
- Fundamental Interactions and Effect of Storage, Ether, Adsorbants and Blood Clotting on Plasma Antithrombin ActivityAmerican Journal of Physiology-Legacy Content, 1952
- The Clot Accelerating Effect of Dilution on Blood and Plasma. Relation to the Mechanism of Coagulation of Normal and Hemophilic BloodBlood, 1951
- THE NATURE OF PLASMA ANTITHROMBIN ACTIVITYBlood, 1950
- ANTITHROMBIN AND HEPARIN IN HUMAN BLOOD1949
- THE NORMAL ANTITHROMBIN OF THE BLOOD AND ITS RELATION TO HEPARINAmerican Journal of Physiology-Legacy Content, 1938
- ON THE ACTION OF HEPARIN AND ITS RELATION TO THROMBOPLASTINAmerican Journal of Physiology-Legacy Content, 1936
- A QUANTITATIVE STUDY ON BLOOD CLOTTING: PROTHROMBIN FLUCTUATIONS UNDER EXPERIMENTAL CONDITIONSAmerican Journal of Physiology-Legacy Content, 1936
- Prothrombase—Its preparation and propertiesProceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character, 1930