Acceleration of fibrin gel formation by unrelated proteins.

Addition of gamma-globulin, serum albumin, hemoglobin, or ovalbumin in concentrations of 1-10 g/dl to solutions of purified fibrinogen results in a substantial (up to six-fold) decrease in the lag time preceding appearance of a firm fibrin gel following addition of thrombin at 24 degrees C. The effect does not appear to be due to a protein-induced enhancement in the enzymatic activity of thrombin, nor does it appear to be due to the co-condensation of the added protein with fibrin/fibrinogen. It is suggested that the observed effect is primarily due to nonspecific volume exclusion arising from increased fractional occupancy of solution volume by macromolecules.