Viscous resistance of thromboid (thrombus-like) surface layers in systems of plasma proteins including fibrinogen

Abstract

Viscous resistance was measured of surface layers which form in systems of bovine and human fibrinogen and other plasma proteins as well as of human plasma and serum. A modification of the Weissenberg rheogoniometer was employed with a combined Couette and cone and plate geometry. The measurements were made at shear rates from 10 3 to less than 10 −1 sec −1, and the torque values, in response to shear, of these polymolecular layers were determined. Fibrinogen solutions gave the highest torque values when compared with γ globulin, while albumin exhibited the least. The higher the concentration of each of the tested proteins, the higher was the torque value. This was also the case with 5 to 90 per cent concentrations of platelet-free oxalate plasma and serum obtained from apparently healthy human subjects. The addition of 0.4 per cent fibrinogen to 0.25 per cent albumin or to 5 per cent plasma or serum increased viscous resistance. Such addition to 5 per cent albumin or usually to 18 per cent plasma showed no change in torque values. A critical concentration of plasma or serum was noted, which ultimately may provide an indicator in the recognition of proneness towards thrombosis and may serve in the management of thrombotic conditions. Preliminary data showed that the surface layers of heparin plasma gave decreased torque values, when compared to the surface layers of oxalate plasma from the same blood withdrawal. These and other findings are discussed in relation to the recently proposed concept of Copley of the initiation of thrombosis, which is based on the formation of polymolecular layers of fibrinogen and other plasma proteins, leading to obstruction of the affected blood vessels. This aggregation of proteins is considered to occur in two steps, viz., a first adsorption process on the endoendothelial fibrin film, followed by a growth process, in which additional protein molecules adsorb on first or previously formed layers of adsorption. Work by other investigators is cited in support of this concept, and in relation to a hitherto unrecognized kind of clotting, viz., the formation of polymolecular layers of plasma proteins including fibrinogen.