KINETIC AND MECHANICAL PARAMETERS OF PURE AND CRYOPRECIPITATE FIBRIN

The kinetics of formation (clot time; CT) as well as a mechanical parameter (breaking strength; BS) of fibrin were measured at various concentrations of fibrinogen. In a pure system and for a fixed level of thrombin, the CT-fibrinogen dependency was biphasic, reaching a minimum in the range 1-8 muM fibrinogen. A new parameter, [Fib]min, the minimal fibrinogen concentration required for phase change, was derived from this. The [Fib]min, values of pure fibrinogen activated with thrombin, ranged between 0.15 and 0.25 muM fibrinogen. Single donor cryoprecipitate (cryo) had similar kinetics and [Fib]min value. A technique for measuring the innate breaking strength of fibrin, independently of its adhesive properties, is described. For pure fibrin activated with thrombin, the BS was a linear function of fibrinogen concentration, with numeric values for the slope of 0.84 ga/muM and slope(Ca) (with 2.5 mM Ca) of 2.26 ga/muM, which transformed into a general description of the BS of fibrin and the fibrinogen level according to the equation: BS = mu [Fib]. The constants mu = 18.9 dyne/muM-cm2 and mu(Ca) = 55.7 dyne/muM-cm2 reflect the innate strength of fibrin clot per cross-section area. Cryo fibrin exhibited a BS equivalent to its fibrinogen level in a pure system. Although scanning electron microscopy of pure and cryo fibrin formed at equivalent fibrinogen levels revealed significant ultrastructural disparity between the pure and cryo fibrin, the kinetics of formation and the mechanical parameters of both were comparable.