The antithrombin activity of human plasma

Abstract

Human thrombin was prepared and its destruction by human defibrinated plasma measured by assaying the amount remaining against fibrinogen. Inactivation continued up to 300 minutes. The reaction did not obey either a 1st or 2nd order equation. Antithrombin could be assayed by measuring the per cent inactivated in the first 10 minutes and referring to a calibration curve. Both antithrombin and thrombin are removed from the system. The antithrombin proved to be in the gamma-globulin electrophoretic fraction, in the albumin fraction on ammonium sulfate and ether precipitation. A method of preparation is described. The activity is stable between pH 6 and 9.5, and up to 50[degree] C, unstable outside these values. pH optimum was about 7.4 and optimal temperature was 55 - 40[degree] C.