We investigated the actions of growth-differentiation factor (GDF)-15, endoglin and N-terminal pro-brain natriuretic peptide (NT-pro-BNP) in 15 male athletes who participated in the ultradistance foot race of the 246 km 'Sparthathlon'. Measurements were performed before (phase I), at the end of the race (phase II) and 48 h post-race (phase III). GDF-15 and endoglin serum concentrations were determined with enzyme-linked immunosorbent assay and NT-pro-BNP plasma levels by electrochemiluminescence. GDF-15 levels were increased from phase I (563.9 +/- 57.1 pg ml(-1)) to phase II (2311.1 +/- 462.3 pg ml(-1)) and decreased at phase III (862.0 +/- 158.0 pg ml(-1)) (p < 0.0002). NT-pro-BNP levels followed a similar pattern to that of GDF-15 from 38.1 +/- 4.8 pg ml(-1) at phase I to 1280.6 +/- 259.0 pg ml(-1) at phase II and 89.8 +/- 13.6 pg ml(-1) at phase III (p < 0.0001) and at the same time points, endoglin levels were 4.7 +/- 0.2 ng ml(-1) at phase I, 5.8 +/- 0.2 ng ml(-1) at phase II and 4.3 +/- 0.2 ng ml(-1) at phase III (p < 0.002). These findings indicate that circulating GDF-15, endoglin and NT-pro-BNP levels reflect a transient endothelial dysfunction in these athletes who participated in a foot race consisting of continuous, prolonged and brisk exercise.