Collagen-bound von Willebrand factor has reduced affinity for factor VIII.

von Willebrand factor (vWf) is a multimeric adhesive glycoprotein that serves as a carrier for factor VIII in plasma. Although each vWf subunit displays a high affinity binding site for factor VIII in vitro, in plasma, only 2% of the vWf sites for factor VIII are occupied. We investigated whether interaction of plasma proteins with vWf or adhesion of vWf to collagen may alter the affinity or availability of factor VIII-binding sites on vWf.

Binding of factor VIII to von willebrand factor is enabled by cleavage of the von Willebrand factor propeptide and enhanced by formation of disulfide-linked multimers.

von Willebrand factor (vWF) is a multimeric adhesive glycoprotein with one factor VIII binding site/subunit. Prior reports suggest that posttranslational modifications of vWF, including formation of N-terminal intersubunit disulfide bonds and subsequent cleavage of the propeptide, influence availability and/or affinity of factor VIII binding sites. We found that deletion of the vWF propeptide produced a dimeric vWF molecule lacking N-terminal intersubunit disulfide bonds.

The effect of subcutaneous injection of unfractionated and low molecular weight heparin on thrombin generation in platelet rich plasma--a study in human volunteers.

We administered a dose of unfractionated heparin (UFH) and two doses of a low molecular weight heparin (LMWH) to healthy volunteers by SC injection. The doses given were: a) UFH, 5000 IU, which represents 8.7 mg of > 5,400 MW active heparin (ACLM) and no < 5,400 active heparin (BCLM), b) enoxaparin 40 mg (3.

Pharmacokinetics and pharmacodynamics of a low molecular weight heparin (enoxaparin) after subcutaneous injection, comparison with unfractionated heparin--a three way cross over study in human volunteers.

We determined, in volunteers, the plasma levels of heparin above and below the critical chainlength necessary for thrombin inhibition (ACLM and BCLM), from 1 to 24 h after subcutaneous injection of 5000 IU unfractionated heparin (UFH), 40 mg enoxaparin and 1 mg/kg body weight of enoxaparin (LMWH) (n = 12 for each dose). The levels were calculated from the antithrombin- and anti-Xa activities using the specific activities of the materials injected. We also determined the course of thrombin- and of factor Xa generation after triggering the extrinsic system in the same samples.

On the relationship between molecular mass and anticoagulant activity in a low molecular weight heparin (enoxaparin).

A low molecular weight heparin (enoxaparin, mean molecular weight approximately 4,400) was separated by gel chromatography into eight different fractions with a narrow distribution around the following mean molecular weights: 1,800, 2,400, 2,900, 4,200, 6,200, 8,600, 9,800 and 11,000. We compared the influence of enoxaparin on the generation of thrombin in plasma to that of the eight fractions. We determined: a) the % of material with high affinity to antithrombin III (HAM) and the % of HAM above the critical chain length necessary to allow for thrombin inhibition (ACLM), b) the specific catalytic activity on the decay of endogenous thrombin, and c) the inhibition of over-all thrombin formation in the extrinsic and the intrinsic pathway.