Coagulation protein function: The influence of acetaldehyde-modified heparin on thrombin activity

Background: The affect of acetaldehyde-treated heparin on thrombin activity has been investigated using factor II-deficient human plasma. Methods: It was observed that 0.021 units of heparin exerts a marked inhibi tion of thrombin activity (1.03 units) as measured by clotting times, prolo nging the clotting times from 9.6 +/- 0.1 seconds to 24.8 +/- 0.1 seconds. However, when the heparin is preincubated with 447 mmoI/L acetaldehyde at R T for 30 minutes prior to mixing with thrombin, a clotting time in excess o f 200 seconds is observed. Clotting times remain elevated with heparin-acet aldehyde mixtures of 89.4, 17.9, 3.6, and 0.72 mmol/L acetaldehyde, with co rresponding clotting times of > 200, 156.0 +/- 2.1, 81.6 +/- 1.0, 38.8 +/- 0.6 seconds, respectively. At 140 mu mol/L acetaldehyde-heparin mixtures, t he clotting time was 17.0 +/- 2.0 seconds. Results: These data support the hypothesis from this laboratory that acetal dehyde-modified heparin enhances coagulation time. They further indicate th at thrombin is targeted by the acetaldehyde-treated heparin. Heparin-acetal dehyde mixtures also reacted with plasma prior to the addition of thrombin to modestly prolong coagulation time. Similarly, but more effectively, thro mbin/heparin mixtures increased the clotting time of acetaldehyde-exposed p lasma. These data further suggest the possibility that reactions of acetald ehyde and heparin are not restricted to those with thrombin, and that they may extend to other blood factors/proteins. Conclusions: The amount of heparin (0.021 units) required to substantially affect clotting time of thrombin (1.03 units) is substantially lower than t hat required to prolong clotting of 0.1 mL of whole plasma (0.36 units), by an order of magnitude. It is inferred that heparin may interact with numer ous cationic proteins or proteins with cationic domains in blood plasma, am ong them being the clotting factors.