Platelet factor 4 enhances fibrin fiber polymerization.

In order to further examine the role of platelet secretory products on fibrin assembly, we have examined the effects of purified platelet factor 4 (PF4) on fibrin formation in vitro. The kinetics of fibrin formation and the structural properties of the resulting fibrin gel are strongly affected by PF4. In the presence of 7.6 ng/mL PF4, the fibrin fiber mass-length ratio increases from 3.5 X 10(12) daltons/cm. These results emphasize the importance of the local microenvironment in clot structure and its subsequent fate at the site of vascular injury.