Summary
Heparin cofactor II (HC II) is a heparin-dependent inhibitor of thrombin, distinct
from antithrombin III (AT III). This study was designed to evaluate its metabolism
in healthy subjects. Purified HC II was labelled with 125I by the lactoperoxidase-glucose
oxidase technique. The biological activity of the HC II was unchanged after labelling
as was its migratory pattern by crossed immunoelectrophoresis in the presence of heparin
or dermatan sulfate.
Three healthy volunteers were injected with 10 uCi and the plasma radioactivity was
measured daily. The data were approximated by a sum of two exponential terms and the
metabolism of HC II was described by a two compartment mamillary system.
The mean values of fractional catabolic rate, intravascular fraction and half-life
of the elimination phase were respectively: 0.44 d-1, 0.60 and 2.53 d. These parameters are of the same order of magnitude as those reported
in the literature for AT III. The plasma HC II concentration in the 3 subjects ranged
from 61 to 82 ug/ml as estimated using our purified preparation. Accordingly, the
absolute catabolic rate ranged from 1.17 to 1.36 mg · kg-1 · d-1.
Keywords
Heparin cofactor II - Metabolism
