Summary
A simple method for biological assay of dermatan sulfate (DS) in plasma is described.
DS accelerates thrombin inhibition by heparin cofactor II (HC II). The principle of
the assay is to measure the residual amidolytic thrombin activity after a short period
of incubation with HC II in defibrinated plasma at low ionic strength. For this method
we take advantage of two observations. Firstly, at fixed concentrations of DS and
of HC II, the rate of thrombin inhibition increases when the ionic strength of the
medium decreases. Secondly, defibrination by bentonite absorption also removes antithrombin
III, HC II and for a large part alpha-2 macroglobulin from the plasma, so that no
other thrombin inhibitor competes with HC II added as a reagent in a second step.
In the conditions described, there is a linear relationship between DS concentrations
in plasma from 0 to 2 μg/ml and the log of residual thrombin activity. The limit of
sensitivity is 0.1 μg/ ml. The assay displays an acceptable reproducibility in intraassay,
inter-assay and inter-individual experiments. It can be used to measure DS in human,
rabbit and rat plasmas. The assay is also sensitive to other HC II activators such
as heparin and pentosan polysulfate.
DS is effective in experimental thrombosis without any detectable anticoagulant effect
ex vivo. Pharmacological concentrations of DS in plasma fall into the range of sensitivity
of this assay, which would be helpful in experimental or clinical studies of DS and
related glycosaminoglycans.
Keywords
Dermatan sulfate - Glycosaminoglycan - Heparin cofactor II
