Electrokinetic studies on fibrinogen. IV. The effect of thrombin and heparin on the fibrinogen-solid interfacial potential

Abstract

Streaming-potential studies were done to evaluate the effect of heparin and also thrombin on the ζ-potential of fibrinogen solutions in contact with capillary surfaces. It is found that unclotted mixtures of thrombin and fibrinogen streamed through clean capillaries have ζ-potentials higher than the fibrinogen in the pH range of 5.5–8. Polymerizing mixtures have ζ-potentials slightly below those for fibrinogen. Heparin is found to increase the ζ-potential of fibrinogenated Teflon and Pyrex capillaries. It is demonstrated that the previous history of the capillary surface influences the extent of these increases. Higher ζ-potentials for mixtures of heparin and fibrinogen are obtained with clean surfaces than with coated capillaries at several pH values. The effect of increasing the heparin concentration in the mixtures streamed through clean capillaries for several fibrinogen concentration levels at pH 7.4 was investigated. It is observed that the ζ-potentials increase to a maximum and remain constant thereafter as the heparin concentration is increased. These results are discussed in terms of electrostatic interaction and a mass-action mechanism.