THE SURVIVAL OF FACTOR VIII (ANTIHEMOPHILIC GLOBULIN) AND FACTOR IX (PLASMA THROMBOPLASTIN COMPONENT) IN NORMAL HUMANS*

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Abstract
A technique has been developed for studying the survival of plasma proteins transfused into normal human recipients. This technique has been applied to a study of the survival of two of the clotting proteins -Factor VIII and Factor IX - in normal humans. The survival curves are biphasic with two exponential components. The first component is interpreted as due to equilibration between intravascular and extra-vascular spaces. The second component is interpreted as the rate of utilization or destruction. For Factor VIII the first phase has a half-life of 3.8 hours; the second phase, a half-life of 2.9 days. For Factor IX, the first phase has a half-life of 15.1 hours; the second phase, a half-life of 8.4 days. The size of the extravascular pool of Factor VIII is approximately 1.5 times the size of the intravascular pool. The extravascular pool for Factor IX is approximately 2.3 times the intravascular pool. The implications of this concept for the therapy of patients with classical hemophilia and Christmas Disease is discussed.