Fluid phase coagulation events have minimal impact on plasma fibrin structure

Reports of altered fibrin structure in clots formed from factor VIII-deficient plasma have raised the possibility that plasma clots mediated by activation of the fluid phase coagulation system might differ from clots formed by the direct addition of thrombin to plasma. In this study, turbidity measurements were used to compare the assembly and structure of clots formed from platelet-poor plasma by either the addition of thrombin or the exposure of recalcified plasma to glass. When clotted by recalcification, the lag phase before initial increase in turbidity was 10 to 25 times longer than when clotted by the addition of thrombin. Decreasing the ionic strength or increasing the calcium concentration shortened the lag phase. At high calcium concentrations (greater than 25 mM) polymerization was delayed and precipitation was noted. pH had a minimal impact over the range of 7.0 to 7.4. Fibrin fiber mass-length ratios for plasma gels formed by activation of the intrinsic cascade were virtually identical to those in gels formed by the direct addition of thrombin. These studies indicate that fluid phase coagulation events before the production of thrombin have a minimal impact on plasma fibrin structure.