| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
von Willebrand factor(VWF) is synthesized in vascular endothelial cells, and released into the plasma as "unusually large" VWF multimers(UL-VWFM), which is degraded by ADAMTS13. Deficiency of ADAMTS13 increases the plasma levels of UL-VWFM, which leads to platelet clumping and/or thrombi formation. VWF antigen(VWF:Ag) in plasma was reported to increase during exercise, but the dynamics on VWT and its degradation on exercise has not been clarified. In order to clarify their homeostatic modulation in vivo, we measured platelet count and plasma values of VWF:Ag, UL-VWFM, ristocetin cofactor(RCof) and ADAMTS13 before and after exercise for 12 hours in 20 healthy male volunteers. Two types of exercise was applied using bicycle ergometer as follows ; 65% VO2 max for 1 hour (hard exercise) and 40% VO2 max for 1 four (mild exercise). As a result, immediately after hard exercise, VWF:Ag and RCof significantly increased, and UL-VWFM was detected, and lasted for 6 hours and disappeared in 12 hour
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s. In contrast, after mild exercise, the increase in VWF was not observed. ADAMTS13 significantly decreased 2 hours after hard exercise and gradually recovered within 5 hours. These findings suggest that the increase in UL-VWFM after hard exercise is due to the compensatory phenomenon to prevent the excessive bleeding at trauma caused by exercise-induced hypertension, followed by the consumption of ADAMTS13 to degrade increased amounts of UL-VWFM. Furthermore, we evaluated the relationship of VWF:antigen to dehydration during exercise because of sweating. As a result, RCof after hard exercise tended to be positively correlated with the degree of sweating per body weight, supporting that the degree of dehydration is closely related to the ability of VWF-dependent platelet aggregation during exercise. These results suggest that enough amount of water intake will be necessary to obtain early physiological response to decrease the platelet aggregation and subsequent occurrence of thrombi formation in small vessels at the recovery phase after exercise. Less
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