The Ability of Thrombin Inhibitors to Reduce the Thrombin Activity Generated in Plasma on Extrinsic and Intrinsic Activation

Abstract

SummaryIn a thrombin generation test with continuous registration of thrombin activity in plasma we studied the ability of a variety of thrombin inhibitors of different type and mechanism of action to influence the activity of thrombin after activation of the coagulation system. Depending on the inhibitor, the peak of thrombin activity is delayed and/or reduced.By blocking the active site of generated thrombin inhibitors cause a concentration dependent reduction of the thrombin peak and inhibit feed-back reactions of thrombin resulting in a delay of thrombin generation. Highly potent synthetic active-site directed inhibitors (Ki ≤ 20 nM) reduce the thrombin activity formed in plasma after extrinsic or intrinsic activation with the same efficiency (IC50 0.1 - 0.6 μM) as hirudin. The delay and reduction of thrombin generation by inhibitors of the anion-binding exosite 1 of thrombin is only attributed to an inhibition of feed-back reactions of thrombin. For a 50% reduction of thrombin activity in plasma by this type of inhibitors relatively high concentrations were determined.

Studies on the Different Modes of Action of the Anticoagulant Protease Inhibitors DX-9065a and Argatroban

“…The previous experimental studies, however, are not consistent with such a mechanism-based, straightforward rationalization. Hirudin and hirulog are known to be specific and direct inhibitors of thrombin, which delay thrombin peaks effectively during coagulation (12,13), yet they do not reduce ETP as effectively as other anticoagulants (12) and display properties similar to those of DX-9065a. Although hirudin is a very potent inhibitor of thrombin, its tight but rather slow binding to thrombin (14) might somehow affect its overall anticoagulant properties in the plasma milieu.…”

Characterization of the plasma and blood anticoagulant potential of structurally and mechanistically novel oligomers of 4-hydroxycinnamic acids

“…TEG assays were performed essentially as reported earlier [17]. Briefly, the assays were initiated by transferring 20 μl of 200 mmol/l CaCl 2 into the hemoscope disposable cup, oscillating through 4° 45′ angle at 0.1 Hz, followed by the addition of a mixture of 340 μl of sodium citrated whole blood containing 10 μl sulfated DHP or dH 2 O (control) at 37°C.…”

Coagulation and Fibrinolysis are in Balance After Moderate Exercise in Middle-aged Participants

“…The release of p-nitroaniline (pNA) was measured at 405 nm during a period of about 16 minutes at intervals of 10 seconds using the microplate reader iEMS-MF 1401 (Labsystems, Helsinki, Finland). The area under the curve (total thrombin potential, TTP) showing the total amount of thrombin generated in the plasma, and the curve that displays after mathematical subtraction of a2M-IIa (the endogenous thrombin potential, ETP), were determined according to Hemker et al 19,20 The method was modified by Prasa et al 21,22 For these tests, the intraassay coefficients of variation were below 3% and interassay coefficients below 4%.…”