STUDIES OF HEMOPHILIA. II. THE ASSAY OF THE ANTIHEMOPHILIC CLOT-PROMOTING PRINCIPLE IN NORMAL HUMAN PLASMA WITH SOME OBSERVATIONS ON THE RELATIVE POTENCY OF CERTAIN PLASMA FRACTIONS 1

Abstract

The quantitative relationship between the coagulation time of shed hemophilic blood and the amt. of normal plasma added to it is described. Extremely minute amts. of normal plasma have a profound effect in accelerating the coagulation of hemophilic blood; as the amt. of normal plasma added is increased the increment in further reduction of the clotting time becomes less and less until the increment is no longer measurable. From the relationship it becomes apparent that in assaying the in vitro clot promoting activity of plasma or plasma protein fractions, the antihemophilic activity of 0.001 ml. of plasma should not be exceeded. The relationship provides a basis for assay of antihemophilic activity of biological materials, thus facilitating separation and purification of the antihemophilic component of normal plasma and study of its properties. Furthermore, the relationship was peculiar to, and constant in, each of 4 hemo-philics studied over a period of from 10 to 23 mo. It is proposed that normal plasma be considered a reference standard in studies aimed at concn. and purification of its antihemophilic clot promoting principle. One antihemophilic unit is defined as that amt. of antihemophilic material which accelerates the coagulation of 2 ml. of hemophilic blood to the same extent as 1 cmm. of avg. fresh citrated plasma. It was found that several samples of plasma protein Fraction I contained only 10-30% of the antihemophilic potency of whole plasma, whereas 100% of the activity was present in the fraction precipitable from diluted plasma by CO2.