T. Nishino et al., Inhibition of the generation of thrombin and factor Xa by a fucoidan from the brown seaweed Ecklonia kurome, THROMB RES, 96(1), 1999, pp. 37-49
The effects of a fucoidan (C-II),which was purified from the brown seaweed
Ecklonia kurome, on the generation of thrombin and factor Xa have been inve
stigated by measuring the amidolytic activities by using the respective spe
cific chromogenic substrates in both plasma and purified systems. C-II inhi
bited significantly the generation of thrombin in both the intrinsic and th
e extrinsic pathways, although the intrinsic inhibitory effect by C-II was
more remarkable than the extrinsic one. On the other hand, C-II was a good
inhibitor of the factor Xa generation in the intrinsic pathway, while it wa
s a poor one in the extrinsic pathway. In the purified systems C-II also in
hibited the formation of prothrombin-activating complex (i.e., prothrombina
se), but not its activity. The concentration of C-II required for 50% inhib
ition of thrombin generation was about one-tenth to one-seventh of that of
the activity of the generated thrombin in plasma. These results indicate th
at C-II has an inhibitory effect on the generation of thrombin by blocking
the formation of prothrombinase and by preventing the generation of intrins
ic factor Xa in addition to its antithrombin activity, and also that the ge
neration-inhibitory effect is more remarkable than C-II's enhancement effec
t on the antithrombin activity by heparin cofactor II in plasma. (C) 1999 E
lsevier Science Ltd. All rights reserved.