Alpha-2-macroglobulin inhibits the anticoagulant action of activated protein C in cord and adult plasma

Healthy newborns have a very low risk of thrombosis, It has been suggested that this is partly due to the anticoagulant effect of alpha-2-macroglobuli n (a2-M). This broad-spectrum protease binding glycoprotein is physiologica lly elevated in newborns over adult values and has been shown to complex ge nerated alpha-thrombin. In our present study, we point out that a2-M also a cts as a procoagulant by inhibiting activated protein C (APC). In all exper iments performed in cord and adult plasma the anticoagulant action of APC w as diminished in a dose-dependent manner when a2-M levels were successively elevated, reflected in increased thrombin potential (TP), and enhanced at low a2-M levels, reflected in decreased TP. Copyright (C) 2001 S. Karger AG , Basel.