Fibrin-blood platelet interaction in a contracting clot.

The interaction of fibrin and blood platelets was studied by measuring tension development in clots containing different ratios of these two components. Isometric tension attained a saturation value (MT) when plotted as a function of the concentration of either component at a constant concentration of the other. The value of MT increases linearly with the minimal platelet concentration (Ps) required in order to reach saturation at various different fibrin concentrations. A linear relationship also holds in a plot of Ps versus the logarithm of the corresponding fibrin concentration. When the cylindrical clots contracted isotonically, the velocity, normalized with respect to the momentary length, was found to be constant. This velocity decreased in an hyperbolic manner with increasing fibrin concentration at a constant concentration of blood platelets. The results are interpreted in terms of a three-dimensional network in which the blood platelets serve as contractile cross-bridges connecting fibrin fibres. Tension development is assumed to be accompanied by the reduction of the angle between fibrin fibres. An attempt was made to calculate the isometric tension developed by a platelet.