von Willebrand factor (VWF) is synthesized in vascular endothelial cells and released into the plasma as “unusually large” VWF multimers (UL-VWFM), which are degraded by VWF-CPase. Deficiency of VWF-CPase increases the plasma levels of ULVWFM, which causes platelet clumping and finally leads to thrombus formation. Plasma VWF antigen (VWF:Ag) has been reported to increase during exercise, but the mechanism underlying this increase remains to be clarified. In this study, we have investigated the relationship between the severity of dehydration induced by sweating during exercise and the changes in plasma VWF levels after exercise. Plasma VWF:Ag was significantly higher immediately (160±15%, p＜0.01) and 2 h after exercise (146±15%, p＜0.01) than the basal value before exercise (101±8%). Ristocetin cofactor (Rcof) was also higher immediately (174±11%, p＜0.001) and 2 h (154±12%, p＜0.01) after exercise than the basal value (117±8%). Plasma VWF-CPase activity was unchanged immediately after exercise (91±3%) compared to the basal value (91±4%), but significantly decreased 2 h after exercise (79±7%). These findings indicate that the imbalance between the early increase in VWF:Ag after exercise and the subsequent decrease in VWF-CPase activity may reflect a predisposing state for the development of cardiovascular events, but conversely the decrease in VWF-CPase activity may play an important role in degrading large amounts of VWF produced and preventing the occurrence of cardiovascular events early after exercise. In addition, no significant correlation was found between various parameters including dehydration rate, heart rate, and maximal oxygen uptake to VWF:Ag and VWF-CPase activity immediately and 2 h after exercise. However, Rcof 2 hour after exercise tended to be positively correlated with the dehydration rate during exercise (p＜0.07), suggesting that severe dehydration might be related to the tendency toward thrombus formation.

DESCENTE SPORTS SCIENCE Vol.28/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE