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PubMed · 8739001

Membrane-based, dry-reagent prothrombin time tests.

S E Zweig·B G Meyer·S Sharma·C Min·J M Krakower·S B Shohet
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Abstract

The authors describe a prototype membrane-based, dry-reagent prothrombin time assay for whole blood. This system uses an asymmetric polysulfone membrane to separate plasma from red blood cells, and works with samples as small as 10 microliters. The membrane contains calcium and thromboplastin, and permits the reactions of the complete extrinsic pathway to occur with minimal distortion from membrane surface interactions. Thrombin generation is monitored optically using a rhodamine-110-based fluorescent thrombin substrate. Fluorescence kinetics are analyzed to produce a prothrombin-time--equivalent parameter that can be converted to an international normalized ratio (INR) value. The system provides results that correlate well with conventional liquid phase prothrombin time assays (R2 = 0.96).

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AnticoagulantsBiocompatible MaterialsBlood CoagulationCalciumErythrocytesFluorescenceFluorescent DyesHumansIndicators and ReagentsMembranes, ArtificialPlasmaPolymersProthrombin TimeRhodaminesSulfonesThrombinThromboplastinWarfarinJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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S E Zweig, B G Meyer, S Sharma, C Min, J M Krakower, S B Shohet. Membrane-based, dry-reagent prothrombin time tests.. https://pubmed.ncbi.nlm.nih.gov/8739001/

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Effect of high- and low-molecular-weight heparins on thrombin-thrombomodulin interaction and protein C activation.

BACKGROUND: Thrombin-thrombomodulin (TM) interaction, which is critical for accelerating the protein C anticoagulant pathway, involves the heparin-like domain of TM. This study was aimed at investigating the possible effect of heparin on thrombin-TM binding and protein C activation. METHODS AND RESULTS: The affinity of thrombin-TM interaction was studied by a functional method, based on the ability of thrombin-TM adduct to activate protein C, and by evaluation of the binding of thrombin to immobilized TM. Both experimental approaches showed that the affinity of thrombin-TM interaction was decreased by micromolar heparin concentrations. Heparin had no significant effect when a recombinant TM form, lacking the chondroitin sulfate moiety, was used. Furthermore, it was also shown that the inhibitory effect of heparin was directly proportional to the heparin molecular mass (molecular weight range, 3 to 16 kDa), which suggests that the effect was mediated by formation of electrostatic bonds between heparin and thrombin. CONCLUSIONS: These results indicate that heparin at therapeutic concentrations reduces the affinity of thrombin for TM and the rate of protein C activation. The magnitude of this effect is proportionally linked to the molecular mass of heparin.

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