The Effect of Calcium Chloride on Anti-Xa Activity of Heparin and Its Molecular Weight Fractions

Summary

The anti-Xa activities of unfractionated heparin (UFH) and nine low molecular weight heparins (LMWH) have been measured in the presence and absence of 3 mM CaCl₂, using bovine Factor Xa, purified human AT III and an amidolytic assay. The addition of CaCl₂ increased the activity of UFH by 93%, but the effect on LMWH was less, ranging from −20% to +55%. Studies of gel filtration fractions of UFH showed marked M_r dependence of the CaCl₂ effect in the range 4,000-12,000. The differences among the various LMW heparins with respect to the effect of CaCl₂ were closely correlated with the amount of polysaccharide above an M_r of 6,500. Kinetic studies confirmed the potentiation of the activity of UFH with bovine Xa and showed an even more marked effect using human Xa.

Keywords

Heparin - LMW heparin - Anti-Xa

• References

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