Post-exercise urinary alpha-1 acid glycoprotein is not dependent on hypoxia

INTRODUCTION: Proteinuria is a transient physiologic phenomenon that occurs with a range of physical activities and during ascent to altitude. Exercise intensity appears to dictate the magnitude of post-exercise proteinuria; however, evidence also indicates possible contributions from exercise-induced hypoxemia or reoxygenation. Utilizing an environmental hypoxic chamber, this crossover designed study aimed to evaluate urinary alpha-1 acid glycoprotein (α1-AGP) excretion pre/post exercise performed in hypoxia and normoxia.

METHODS: Sixteen individuals underwent experimental sessions in normoxia (NOR, 20.9% O2) and hypoxia (HYP, 12.0% O2). Sessions began with a 2-hour priming period before completing a graded maximal exercise test (GXT) on a cycle ergometer, which was followed by continuation of exposure for an additional 2 hours. Physiologic responses (i.e., blood pressure, heart rate, and peripheral oxygenation), Lake Louise Scores, and urine specimens (analyzed for albumin and α1-AGP) were collected pre- and post-exercise (after 30, 60, and 120 minutes).

RESULTS: Peak power output was significantly reduced in HYP (193 ± 45 W) compared to NOR (249 ± 59 W, p < 0.01). Post-exercise urinary α1-AGP was greater in NOR (20.04 ± 14.84 μg•min-1) compared to HYP (15.08 ± 13.46 μg•min-1), albeit the difference was not significant (p > 0.05). Changes in urinary α1-AGP from pre- to post-30 minutes were not related to physiologic responses or performance outcomes observed during GXT in NOR or HYP.

CONCLUSION: Despite profound systemic hypoxemia with maximal exercise in hypoxia, post-exercise α1-AGP excretion was not elevated above levels observed following normoxic exercise.