Studies of anti-Xa activity in human plasma II: The role of lipoproteins
1982; Elsevier BV; Volume: 27; Issue: 2 Linguagem: Inglês
10.1016/0049-3848(82)90198-0
ISSN1879-2472
AutoresTrevor W. Barrowcliffe, C A Eggleton, J. Stocks,
Tópico(s)Trauma, Hemostasis, Coagulopathy, Resuscitation
ResumoThe major plasma inhibitor of Factor Xa is thought to be anti-thrombin III (At III). However, adsorption of plasma by aluminium hydroxide (A1(OH)3) increases its rate of neutralisation 7–8 fold, and this ‘fast-acting’ anti-Xa activity has been shown to be independent of At III. Gel filtration of plasma indicated that the anti-Xa activity after Al(0H)3 adsorption was located largely in the high molecular weight (> 200,000) fractions, which contain most of the plasma lipoproteins. Purified lipoproteins of very low-density (VLDL), low-density (LDL) and high density (HDL) were prepared by ultracentrifugation and their anti-Xa activities measured before and after adsorption by Al(OH)3. Both LDL and HDL had significant anti-Xa activities by clotting and amidolytic assays. Al(OH)3 adsorption of LDL and HDL gave a marked increase in anti-Xa clotting activity and a decrease in amidolytic activity. Incubation of the adsorbed lipoproteins with phospholipase enzymes destroyed the anti-Xa activity, and prior incubation of Factor Xa with Ca++ and phospholipid protected it against inactivation, indicating that the anti-Xa activity of the adsorbed lipoproteins is mediated via binding of Xa to phospholipid in the lipoproteins. These results indicate that lipoproteins, especially LDL and HDL, are responsible for the increased anti-Xa activity of plasma after Al(OH)3 adsorption. These lipoproteins appear to contain high affinity phospholipid binding sites for Xa which are revealed by Al(OH)3 adsorption.
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