Title: Crosslinking of von Willebrand factor to fibrin by factor XIII (2)
Abstract: It has been previously reported that von Willebrand factor (vWF) was incorporated into fibrin clot by factor XIIIa (F. XIIIa) in delayed blood coagulation process. In the present study, the effects of F. XIIIa concentration and clotting time on the incorporation reaction of vWF into fibrin clot were observed, and then the incorporation mechanism besed on the F. XIIIa dependent crosslinking of vWF into fibrin clot was analyzed by using 131I-fibrinogen and 125I-vWF in purified system.Constant amount of F. XIIIa was added into fibrinogen-vWF mixture contained various concentration of hirudin to elongate clotting time, and then, the amount of vWF incorporated in clot was measured by radioactivity after incubation for 18 hours. It was recognized that vWF incorporation tended to increase in proportion to the delayed clotting time and depended on F. XIIIa concentration (Fig. 1). To elucidate the mechanism of vWF incorporation, SDS-PAGE was performed on the clot which was reduced and dissolved with urea-SDS-DTT, and radioactivity of each sliced gel was counted. Radioactive analysis with 131I-fibrinogen and 125I-vWF proved that vWF was crosslinked to α-chain and entered into high molecular weight α-polymer (Fig. 2).