Summary
Turbidimetric studies indicate that Zn(II) accelerates fibrin gelation [decreases
clotting time (CT)] and increases maximal fibrin clot turbidity. For any given level
of fibrinogen (0.2-2.6 mg/ ml), the relative fibrin turbidity of thrombin-induced
clots increases with Zn(II) in a concentration dependent manner. Zinc-associated turbidity
increases are also observed in the presence of 2 mM Ca(II). With citrate, similar
turbidity increases are observed, though at higher cation levels. Thus, turbidimetry
indicates that the gel formed with Zn(II) is coarser, or has thicker fibre strands.
SEM micrographs confirm that fibre thickness ranges from 260 Å to 2600 Å, when Zn(II)
levels range from 0-50 uM. With citrate, TEM micrographs reveal amore than 20 x fold
increase in fibre diameter (100 Å->2000 Å) with higher Zn(II) (<1 mM) levels. Based
on a fibrin monomer cross-section of ~60 Å, the electron micrographs indicate that
depending on the Zn(II) levels, fibrin strands are composed of between 2 to 40 monomeric
fibrin molecules. Thus, at physiologically relevant levels, Zn(II) can drastically
modulate fibrin ultrastructure.
Keywords
Fibrin - Turbidity - SEM - TEM - Fibre diameter
