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RC Friedberg, PO Hagen and SV Pizzo
Department of Pathology, Duke University Medical Center, Durham, NC 27710.
The role of endothelium in the inhibition of human factor Xa was studied in
a plasma environment. Human factor Xa can bind to and function on bovine
aortic endothelium in a manner similar to that of bovine factor Xa.
Approximately 70% of the bound factor Xa is subject to inhibition by plasma
proteinase inhibitors, and the remaining 30% is irreversibly bound as part
of a 125 Kd membrane-associated complex not subject to proteolytic
degradation. The proportion reversibly bound and its rate of release do not
alter with changes in calcium, citrate, heparin, or active proteinase
inhibitor concentrations. The principal plasma proteinase inhibitor of
human factor Xa was antithrombin III, which accounted for 60% to 65% of
factor Xa released from endothelium, with alpha 1-proteinase inhibitor
inactivating 20% to 25% and alpha 2- macroglobulin approximately 15%. All
of the reversibly bound factor Xa was identified in complex with one of
these three proteinase inhibitors. The thrombin active-site inhibitor
hirudin was found to markedly accelerate the displacement of reversibly
bound factor Xa from the endothelium and to associate specifically with
factor Xa without a loss of activity toward chromogenic substrates, perhaps
accounting for a novel mechanism of anticoagulation.
This article has been cited by other articles:
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| Copyright © 1988 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
