INTRODUCTION: In competitive sports, high altitude training is used to increase EPO concentrations and the number of erythrocytes and thus to improve O2-transport capacity in blood. Additionally, hypoxia seems to be a powerful Stimulus for angiogenesis because vascular growths factors (e.g. VEGF), are also controlled by HIF-1a. Cytokines, especially IL-6 is discussed as an "exercise factor", which could mediate some of the exercise-induced metabolic changes, which appear to be intensity dependent. The aim of this study was to examine the acute effects of hypoxia and exercise on growth factor secretion. METHOD: Seven subjects participated in this study. Each subject was exposed to 5 different conditions for 90 min. Condition 1: Normobaric hypoxia (2000m); Condition 2: Normobaric hypoxia (4000m); Condition 3: Cycling exercise at sea level; Condition 4: Cycling exercise under normobaric hypoxia (2000m); Condition 5: Cycling exercise under normobaric hypoxia (4000m). Blood samples were taken pre, 0h and 3h after altitude/exercise. Afterwards angiogenic/vasculogenic growth factor concentrations (EPO, VEGF, IL-6, IL-8, IGF-1) were measured by ELISA. RESULTS: EPO (2000m, 4000m) and IL-6 (NN, 2000m, 4000m) showed a significant increase 3h and 0h after exercise respectively. For IL-8, IGF-1 and VEGF no changes were measured for any condition. DISCUSS1ON: IL-6 serum levels are exercise dependent, whereas hypoxia has no additional effect. Although EPO and VEGF are both regulated by HIF-1a the growth factors do not show similar reactions. To achieve an increase in EPO levels, hypoxia has to be combined with exercise. It appears as if the exercise stimuli/hypoxia is not intense enough to change VEGF, IGF-1 and IL-8 serum levels. CONCLUSION: This study shows that- under the chosen conditions - hypoxia alone seems to be a weak Stimulus to induce changes in serum growth factor/cytokine levels. To achieve these changes hypoxia has to be combined with exercise, whereas exercise intensity should be rather high. Exercise intensities and the degree of hypoxia required for a growth factor release should be investigated further.
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