BACKGROUND Physical inactivity increases the risk of atherosclerosis. However, the molecular mechanisms of this relation are poorly understood. A recent report indicates that endostatin, an endogenous angiostatic factor, inhibits the progression of atherosclerosis, and suggests that reducing intimal and atherosclerotic plaque tissue neovascularization can inhibit the progression atherosclerosis in animal models. We hypothesize that exercise can elevate the circulatory endostatin level. Hence, exercise can protect against one of the mechanisms of atherosclerosis. RESULTS We examined treadmill exercise tests in healthy volunteers to determine the effect of exercise on plasma levels of endostatin and other angiogenic regulators. Oxygen consumption (VO2) was calculated. Plasma levels of endostatin, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) were determined using ELISA. The total peak VO2 (L) in 7 male subjects was 29.5 +/- 17.8 over a 4-10 minute interval of exercise. Basal plasma levels of endostatin (immediately before exercise) were 20.3 +/- 3.2 pg/ml, the plasma levels increased to 29.3 +/- 4.2, 35.2 +/- 1.8, and 27.1 +/- 2.2 ng/ml, at 0.5, 2, and 6 h, respectively, after exercise. There was a strong linear correlation between increased plasma levels of endostatin (%) and the total peak VO2 (L) related to exercise (R2 = 0.9388; P < 0.01). Concurrently, VEGF levels decreased to 28.3 +/- 6.4, 17.6 +/- 2.4, and 26.5 +/- 12.5 pg/ml, at 0.5, 2, and 6 h, respectively, after exercise. There were no significant changes in plasma bFGF levels in those subjects before and after exercise. CONCLUSIONS The results suggest that circulating endostatin can be significantly increased by exercise in proportion to the peak oxygen consumption under physiological conditions in healthy volunteers. These findings may provide new insights into the molecular links between physical inactivity and the risk of angiogenesis dependent diseases such as atherosclerosis.