Blood, 1963, Vol. 21, No. 2, pp. 221-236.
© 1963 American Society of Hematology, Inc.
The Importance of Activation of Antihemophilic Globulin
and Proaccelerin by Traces of Thrombin in the Generation
of Intrinsic Prothrombinase Activity
SAMUEL I. RAPAPORT 1,
SANDRA SCHIFFMAN 1,
MARY JANE PATCH 1, and
SARA BETH AMES 1
1 Departments of Medicine and Biochemistry, University of Southern California
School of Medicine, Los Angeles, Calif.
There are two major time-consuming steps in intrinsic clotting in vitro.
The importance of the first step—the triggering of intrinsic clotting through
the generation of activation product (AP) activity—has been appreciated
for several years. This paper has been concerned with the delineation of the
second important time-consuming step—the generation of a trace of thrombin,
which by activating both anti-hemophilic globulin (AHG, factor VIII ) and
proaccelerin (factor V ), shifts the intrinsic clotting process into high gear.
Data have been presented which indicate that when plasma contains AP,
activated AHG (AHG'), activated proaccelerin (accelerin ) and free platelet
factor 3-like activity, all of the remaining reactions required to generate powerful intrinsic prothrombinase activity take place within 7 to 12 seconds after
recalcification. It may well be that AHG and proaccelerin must be activated
by minute traces of thrombin before they can participate effectively in the
generation of intrinsic prothrombinase activity.
Submitted on May 14, 1962
Accepted on October 24, 1962
