Postexercise urinary alpha-1 acid glycoprotein is not dependent on hypoxia

Proteinuria is a transient physiological phenomenon that occurs with a range of physical activities and during ascent to altitude. Exercise intensity appears to dictate the magnitude of postexercise proteinuria; however, evidence also indicates the possible contributions from exercise-induced hypoxemia or reoxygenation. Using an environmental hypoxic chamber, this crossover-designed study aimed to evaluate urinary alpha-1 acid glycoprotein (alpha 1-AGP) excretion pre/postexercise performed in hypoxia (HYP) and normoxia (NOR). Sixteen individuals underwent experimental sessions in normoxia (NOR, 20.9% O-2) and hypoxia (HYP, 12.0% O-2). Sessions began with a 2-h 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 h. Physiological responses (i.e., blood pressure, heart rate, and peripheral oxygenation), Lake Louise Scores (LLSs), and urine specimens (analyzed for albumin and alpha 1-AGP) were collected pre- and postexercise (after 30, 60, and 120 min). Peak power output was significantly reduced in HYP (193 +/- 45 W) compared with NOR (249 +/- 59 W, P < 0.01). Postexercise urinary cd-AGP was greater in NOR (20.04 +/- 14.84 mu g.min(-1)) than in HYP (15.08 +/- 13.46 mu g.min(-1)), albeit the difference was not significant (P > 0.05). Changes in urinary alpha 1-AGP from pre- to post-30 min were not related to physiological responses or performance outcomes observed during GXT in NOR or HYP. Despite profound systemic hypoxemia with maximal exercise in hypoxia, postexercise alpha 1-AGP excretion was not elevated above the levels observed following normoxic exercise. NEW & NOTEWORTHY By superimposing hypoxic exposure and maximal exercise, we were able to investigate the impact of hypoxia on postexercise proteinuria. Urinalysis for alpha 1-AGP (via particle-enhanced immunoturbidimetry) in specimens collected pre-/postexercise enabled the sensitive detection of altered glomerular permeability. Data indicated that exercise intensity, rather than the degree of exercise-induced hypoxemia, determines postexercise proteinuria.