Study of anticoagulant mechanism of low molecular weight heparin.
The binding ability of low molecular weight heparin (FR-860), and conventional unfractionated heparin (UF-heparin) to factor Xa (F.Xa), thrombin and AT III was investigated using FR-860- and UF-heparin-Sepharoses. FR-860 could not bind directly to F.Xa. FR-860 bound to thrombin and AT III with stronger affinity to AT III than to thrombin. On the other hand, UF-heparin bound to F.Xa, thrombin and AT III with the strongest affinity to AT III followed by thrombin and F.Xa. AT III mediated the binding between F.Xa and FR-860 and accelerated the reaction between F.Xa and UF-heparin. On the other hand, AT III did not affect the binding between thrombin and FR-860 or UF-heparin. Diisopropyl fluorophosphate-treated thrombin inhibited the binding between AT III and FR-860, but not that between AT III and UF-heparin. These results suggest that the anti-F.Xa activity of FR-860 is mediated by AT III. Furthermore, the difference of antithrombin activity between FR-860 and UF-heparin depends on the capability to form ternary complex of FR-860 or UF-heparin, AT III and thrombin.
Hamano
S
S
Pharmacological Laboratories, Kissei Pharmaceutical Co. Ltd., Hotaka, Japan.
Nishiyama
M
M
Komatsu
H
H
Miyata
H
H
Ikeda
S
S
Sakuragawa
N
N
D000818:Animals; D000990:Antithrombin III / Q000378:metabolism*; D002846:Chromatography, Affinity; D015944:Factor VIIIa / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology*; D006495:Heparin, Low-Molecular-Weight / Q000378:metabolism / Q000494:pharmacology*; D007531:Isoflurophate / Q000031:analogs & derivatives / Q000494:pharmacology; D011485:Protein Binding; D011817:Rabbits; D012685:Sepharose; D013917:Thrombin / Q000378:metabolism* / Q000494:pharmacology
D006495:Heparin, Low-Molecular-Weight; D007531:Isoflurophate; D015944:Factor VIIIa; D000990:Antithrombin III; D006493:Heparin; D012685:Sepharose; C027798:DFP-alpha-thrombin; D013917:Thrombin