D. Brieger et J. Dawes, LOW-MOLECULAR-WEIGHT HEPARIN IS RESPONSIBLE FOR THE ANTI-XA ACTIVITY OF DESMIN-370, Thrombosis and haemostasis, 75(2), 1996, pp. 286-291
Dermatan sulphate does not catalyse the inactivation of factor Xa. How
ever, the low molecular weight (LMW) dermatan sulphate Desmin 370 has
been shown to generate circulating anti-Xa activity following administ
ration to humans. Using a single batch of Desmin 370, we measured 3 U/
mg of anti-Xa activity by amidolytic assay in vitro. The material resp
onsible for this activity had a lower molecular weight range (6000 and
1800 Dal than Desmin 370 and was more highly sulphated than the bulk
of the drug. Heparinase digestion of Desmin 370 eliminated 90% of the
in vitro anti-Xa activity without significantly interfering with its a
bility to potentiate inactivation of thrombin by HCII, suggesting that
the anti-Xa activity is not due to dermatan sulphate and is probably
heparin. When I-125-labelled Desmin 370 together with 40 mg/kg carrier
drug was administered intravenously to a rabbit, anti-Xa activity was
readily detectable in the plasma for up to 10 h and had a longer half
-life than the sulphated radiolabel. h lost of this anticoagulant acti
vity was recovered from the plasma by Polybrene affinity chromatograph
y and was probably a sulphated glycosaminoglycan. Administration of th
e heparinase-digested drug to a rabbit resulted in 70% less anti-Xa ac
tivity than the undigested drug. We conclude that Desmin 370 contains
detectable quantities of biologically active low molecular weight hepa
rin, which is responsible for persistent anti-Xa activity following in
travenous administration.