Turnover of *I-protein C inhibitor and *I-alpha 1-antitrypsin and their
complexes with activated protein C
M Laurell, J Stenflo and TH Carlson
Department of Clinical Chemistry, Malmo General Hospital, Sweden.
The rates of clearance and catabolism of human protein C inhibitor (PCI)
and human alpha 1-antitrypsin (alpha 1-AT) and their complexes with human
activated protein C (APC) were studied in the rabbit. The
radioiodinated-free inhibitors had biologic half-lives of 23.4 and 62.1
hours, respectively, while the corresponding *I-labeled activated- protein
C complexes were cleared with half-lives of 19.6 +/- 3.1 and 72.2 +/- 6.1
minutes. Complex clearances were linked to their catabolism as shown by a
correlation between clearance and the appearance of free radioiodine in the
plasma. Thus, the difference in the rates of catabolism would result in a
fivefold greater amount of alpha 1-AT-APC complex than PCI-APC complex 1
hour after the formation of equal amounts of these in vivo. These results
lead to the conclusion that the relative contribution of PCI and alpha 1-AT
to the physiologic inhibition of APC cannot be determined only from the
rates of the formation of these complexes in vitro, or from measurement of
their levels in plasma. The APC-PCI complex is unstable as compared with
the APC-alpha 1-AT complex, compounding the problem of estimating rates of
complex formation from their levels in plasma.
Volume 76,
Issue 11,
pp. 2290-2295,
12/01/1990
Copyright © 1990 by The American Society of Hematology
