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Abstract
Lysis of clots prepared from native or citrated whole blood as measured by release
of 125I fibrinogen degradation products was 10% or less at 20 hours. Lysis of these clots
was accelerated by activated protein C in a dose-dependent manner (0.1 to 20 μg/ml)
from less than 10% to 60–80% at 20 hours. Lysis of clots prepared from native or citrated
platelet poor plasma across the same concentration range of activated protein C was
less than 15%. Gla-domainless activated protein C was equally effective in accelerating
clot lysis whereas DIP-activated protein C or factor Xa did not accelerate clot lysis.
This suggested that this action of activated protein C was enzymatic and this this
action was limited to protein C among the vitamin K dependent proteins.
The unresponsiveness of platelet poor plasma to activated protein C was completely
restored to that of whole blood by addition of mononuclear leukocytes. Addition of
red corpuscles or platelets
had no effect on this response, while addition of polymorphonuclear leukocytes partially
restored this response. Addition of metabolic inhibitors 2-deoxyglucose and oligomycin
inhibited the response of whole blood and of plasma-mononuclear leukocytes to activated
protein C. Reconstitution studies of platelet poor plasma made deficient in plasminogen
activator and plasminogen showed that accelerated clot lysis produced by mononuclear
leukocytes and activated protein C required the presence of plasminogen. We concluded,
therefore, that activated protein C accelerates whole blood or plasma-leukoycte clot
lysis by modulating activation of the plasminogen system by metabolically active leukocytes.

Keywords
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Article info
Publication history
Accepted:
December 18,
1984
Received:
October 16,
1984
Identification
Copyright
© 1985 Published by Elsevier Inc.