Zinc alters fibrin ultrastructure.

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 A to 2600 A, when Zn(II) levels range from 0-50 uM. With citrate, TEM micrographs reveal a more than 20 X fold increase in fibre diameter (100 A- greater than 2000 A) with higher Zn(II) (less than 1 mM) levels. Based on a fibrin monomer cross-section of approximately 60 A, 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.