| Research Abstract |
The rare earth metals, including lanthanum (La) , cerium (Ce) , neodymium (Nd) , samarium (Sm) , terbium (Tb) , dysprosium (Dy) , erbium (Er) and ytterbium (Yb) , are remarkably noteworthy as new industrial materials in the pioneering technological industries.Although the use of rare earth metals is increasing, there are very few reports on the biological effects of these metals.Therefore, this study was designed to detetermine the effects of these rare earth metals on blood coagulation in vitro.The clotting assay was performed by the method of Furie et al. (J.Biol.Chem., 251 : 3235,1976) and the enzymatic activites were determined with the method of Kawabata et al. (Eur.J.Biochem., 172 : 17,1998) .La, Ce, Nd, Sm, Tb, Dy, Er and Yb prolonged the clotting time of normal human plasma in a dose-dependent manner when clotting was induced either by thromboplastin or by kaolin in the presence of cephalin and Ca2+.They also prolonged the activated factor X induced clotting time of platelet-rich plasma.The amidolytic activaties of activated factor X and thrombin progressively decreased with increasing amount of rare earth metals.These results suggested that the rare earth metals, La, Ce, Nd, Sm, Tb, Dy, Er and Yb, appear to show their anticoagulant effects with mechanisms in part the inhibition of the enzymatic activities of both activated factor X and thrombin.
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