Summary
In this study highly reproducible turbidimetric techniques are used to investigate
clotting of human platelet-poor plasma and purified human fibrinogen solutions by
thrombin. Three phases are clearly distinguishable turbidimetrically during clotting.
All the three phases are altered by dextran. This effect of dextran is not mediated
by any action on the enzymatic activity of thrombin. Further, it is independent of
the molecular weight of dextran, but is found related to the final dextran, thrombin
and fibrinogen concentrations. Evidence is presented to show that dextran accelerates
the polymerisation of fibrin monomer. However, it seems clear that dextran has an
additional action quite apart from this effect. These actions of dextran are discussed
in relation to kinetics of clot formation.
