Binding of plasma von Willebrand factor by arterial microfibrils

We developed an ELISA test to measure the binding of plasma von Willebrand factor (vWF) to arterial microfibrils and compared this interaction to the binding of vWF to collagen under the same conditions. We found that vWF binds to microfibrils in a similar manner as it binds to collagen: the binding was independent of the presence of cations, and temperature of incubation and was displaced by 1 M NaCl. Using purified 125I-vWF we showed that the binding was saturable and could be displaced by cold vWF in excess. Using immunoblotting we showed that vWF binds to a 97 kDa protein present in the microfibrils different from the 128 kDa thrombospondin-like structure (GP 128) which in microfibrils is known to interact with blood platelets. These results indicate that in the subendothelium, microfibrils bind plasma vWF and this reinforces the thrombogenic role of these structures.