The Time Course Of Endogenous Erythropoietin, Il-6, And Tnf Alpha In Response To Acute Hypoxic Exposures

Erythropoietin (EPO) rapidly decreases on return to sea level (SL) after chronic altitude exposure. Acute hypoxia may provide an additional stimulus to prevent the decline in EPO. Proinflammatory cytokines, interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) have been shown to inhibit EPO production. Optimal normobaric hypoxic exposure has not been established; therefore, investigation of methods eliciting the greatest response in EPO to limit physiological stress is required. Eight men (age 27 +/- 4years, body mass 77.5 +/- 9.0kg, height 179 +/- 6cm) performed four passive exposures to different normobaric hypoxic severities [FiO(2): 0.209 (SL), FiO(2): -0.135 (3600m), FiO(2): -0.125 (4200m) and FiO(2): -0.115 (4800m)] in a hypoxic chamber for 2h. Venous blood was drawn pre-exposure and then at 1, 2, 4, 6, and 8h to determine EPO concentration ([EPO]), IL-6, and TNF alpha. During 4200 and 4800m, [EPO] increased from 5.9 +/- 1.5 to 8.1 +/- 1.5 mU/mL (P=0.009) and 6.0 +/- 1.4 to 8.9 +/- 2.0 mU/mL (P=0.037), respectively, with [EPO] increase peaking at 4h (2h post-exposure). There were no differences in IL-6 or TNF alpha during or post-exposure. Increased [EPO] was found 2h post hypoxic exposure as result of 2h of normobaric hypoxia 4200m. There was no dose-response relationship in [EPO] between simulated hypoxia severities.