Coagulation protein function VI: augmentation of anticoagulant function by acetaldehyde-treated heparin.

Acetaldehyde (AcH) at preincubation concentrations of 447, 89.4, and 17.9 mM potentiates the effects of heparin on the clotting time of plasma. While control plasma clotted in the range of 12.6+/-0.1 to 13.8+/-0.1 sec, and heparin-treated plasma clotted in a range from 131.5+/-2.5 to 168.2+/-1.2 sec, heparin that was preincubated at room temperature for 30 min with 89.4 or 447 mM AcH did not clot plasma in 300 sec. Heparin exposed to 17.9 mM AcH clotted plasma in 193+/-1.1 sec. Ethanol at a 404 mM concentration also prolonged the clotting time of heparin-treated plasma >300 sec, while 202 mM ethanol prolonged the clotting time of heparin-treated plasma from 149.0+/-2.0 sec to 219.5+/-1.7 sec. It is suggested that AcH alters the tertiary structure of heparin by adduct formation, possibly by formation of cyclic acetals with iduronic and glucuronic acids, thereby more readily affecting binding of the glycosaminoglycan to antithrombin III and/or thrombin, prolonging clotting time. Ethanol, which does not react covalently with heparin, might affect its conformation as a consequence of an organic solvent effect. Protamine sulfate prolonged the clotting time of plasma from 13.6+/-0.1 sec to 17.9+/-0.2 sec. Protamine sulfate-treated heparin clotted plasma in 21.0+/-0.4 sec relative to heparin-treated plasma (160.4+/-1.7 sec). In subsequent experiments, AcH-treated protamine sulfate extended the clotting time of protamine sulfate from 17.9+/-0 sec to 33.7+/-0.6 sec. Prior addition of protamine sulfate to AcH-heparin mixtures or heparin to protamine sulfate-AcH mixtures before addition to plasma resulted in clotting times of 22.0+/-0.4 sec and 24.1+/-0.5 sec, respectively, relative to control clotting times of 162.3+/-2.6 sec for plasma-heparin mixtures. These results confirm both the reduction in coagulation time of heparin-treated plasma by protamine sulfate and the prolongation of clotting time of plasma by protamine sulfate. Furthermore, and importantly, they indicate that acetaldehyde-treated protamine sulfate is a more effective anticoagulant than protamine sulfate. It is suggested that reversible adduct formation between acetaldehyde, heparin, and protamine sulfate may occur as a means explaining the essentially identical coagulation time of these mixtures when added to plasma regardless of the order of premixing. Ethanol (404 mM) did not influence protamine sulfate effects. Lastly, the potentiation of the anticoagulant function of heparin by acetaldehyde suggests that a structural modification of the glycosaminoglycan may occur in alcoholics.