Tissue plasminogen activator and plasminogen activator inhibitor-1 gene expression in muscle after maximal acute aerobic exercise

Animal studies suggest plasminogen activation in skeletal muscle is necessary for muscle repair. However, plasminogen activators have been studied little in humans. Therefore, the purposes of this study were to: 1) assess changes in skeletal muscle gene expression of fibrinolytic and coagulation factors 2) assess plasma activity of tPA and PAI-1 in response to an acute bout of maximal aerobic exercise, 3) determine if there is any relationship between muscle gene expression of tPA and PAI-1 with plasma activity levels. Six healthy, college-aged males volunteered blood and muscle samples prior to and immediately following a maximal treadmill exercise test. Muscle tissue was homogenized and purified RNA underwent RT-PCR using gene-specific primers for tPA and PAI-1 as well as biotynylation for microarray. Blood was analyzed via biofunctional immunosorbent assays for tPA and PAI-1 activity. A significant increase in tPA mRNA was seen with exercise (p = 0.038) while PAI-1 mRNA showed no changes with the exercise. Muscle tPA activity showed no changes with the exercise bout. Plasma tPA showed a significant increase in activity (p < 0.0001) while plasma PAI-1 activity had no change with the exercise bout. In conclusion, tPA synthesis increases in muscle following acute, high-intensity exercise and muscle production does not significantly contribute to plasma tPA increases seen with acute, high-intensity exercise. Key Words: Microarray, Muscle Regeneration, Zymography, Coagulation, Fibrinolysis