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Inhibition of thrombin generation by heparin and low molecular weight (LMW) heparins in the absence and presence of platelet factor 4 (PF4)
Author(s) -
Padilla Ana,
Gray Elaine,
Pepper Duncan S.,
Barrowcliffe Trevor W.
Publication year - 1992
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1992.tb06437.x
Subject(s) - thrombin generation , heparin , thrombin , platelet factor 4 , platelet , low molecular weight heparin , pharmacology , chemistry , medicine
S ummary . The ability of several low molecular weight (LMW) heparins and unfractionated heparin (UFH) to inhibit thrombin generation, and their anti‐Xa and anti‐IIa activities, were measured in the absence and presence of platelet factor 4 (PF4). The LMW heparins studied were 2–5 times less potent, on a weight basis, than UFH as inhibitors of thrombin generation in platelet‐poor plasma: the inhibition of thrombin generation by LMW heparins correlated better with their anti‐IIa activity ( r = 0–98) than with their anti‐Xa activity ( r = 0–69). At low concentrations of PF4. the activity of LMW heparins in the thrombin generation test was neutralized less than that of UFH. but at higher PF4 concentrations all their activities could be neutralized except in anti‐Xa assays. These observations support the hypothesis that anti‐IIa activity is important for inhibition of thrombin generation by LMW heparins in vitro. However, when all the anti‐IIa activity of LMW heparins was neutralized by PF4. considerable inhibitory activity remained in thrombin generation and anti‐Xa assays, indicating that a portion of the anti‐Xa activity of LMW heparins also contributes towards inhibition of thrombin generation.