Comparative Hemorheological and Biochemical Studies of a Bovine Fibrinogen

Among numerous fibrinogen (Fg) preparations of different mammalian origins (human, bovine, sheep, rabbit, cat) in measurements of viscous resistance -VR- (torque values, τ, dyne, cm) of surface layers (SLs), we found as an exception a bovine Fg, FgSM (Schwarz-Mann, Orangeburg, N.Y. Lot # Y1013), which did not show measurable VR at shear rates (SRs) from 10^-3 to 10^-1 sec^-1 without prior application of high shearing forces (hSF). This led to biochemical characterization, in which FgSM did not exhibit any significant difference in chain structure, as compared with highly purified Fg showing high τ, indicating that a dialysable component in the FgSM was responsible for the inhibition of VR. Our biochemical studies could not detect significant differences between the FgSM and Fg from other sources. A hSF at 1000 sec^-1 for 3 min was then applied prior to the rheological tests at low SF from 10^-3 to 10^-1 sec^-1. This procedure always resulted in significant increases in VR of SLs of all Fg preparations, including the FgSM. High shear, which exists at the vessel wall in vivo, is particularly high in the microcirculation and is also augmented in vortex and disturbed flow at sites of branchings, bends and bifurcations in the vascular system. The hSF may contribute to the initiation of thrombus formation due to the proposed progressive adsorption of Fg, layer upon layer, at these sites (Copley, Biorheol. 8, 79, 1971; Microvasc. Res. 8, 192, 1974). A further hypothesis is introduced in which the polymerization sites of the Fg molecule are unfolded by the hSF at the vessel wall, resulting in intravascular polymerization of Fg

(Aided in part by Office of Naval Research Contract # N00014-75-C-0222 )