Prothrombin homeostasis in cross-circulated normal and Dicumarol-treated dogs

¹ Department of Pathology, University of North Carolina, Chapel Hill, North Carolina

A series of experiments was done using the technique of cross circulation to study the fate of plasma prothrombin. Arteriovenous shunts of polyethylene tubing were made between normal dogs and dogs made prothrombin-deficient by administering Dicumarol. The shunts were maintained for as long as 4 hr. Prothrombin activity of the plasma of each dog was determined at intervals throughout the cross circulation and recovery period. The immediate effect of this procedure is simple dilution of the plasma prothrombin of the normal dog with the prothrombin-deficient plasma of the Dicumarol-treated animal. After cross circulation, prothrombin returns slowly to the plasma of the normal dog. These studies indicate that prothrombin is not present in extravascular sites in amounts sufficient to influence plasma prothrombin activity. Prothrombin was maintained in the plasma of the Dicumarol-treated dog only a few hours. Equilibration of plasma prothrombin with extravascular fluids does not appear to be the primary factor in this rapid loss of acquired plasma prothrombin activity.