Influence of N-acetylcysteine administration on pulmonary O2 uptake kinetics and exercise tolerance in humans

• Published in: Respiratory physiology & neurobiology Vol. 175; no. 1; pp. 121 - 129
• Main Authors: Bailey, Stephen J., Winyard, Paul G., Blackwell, Jamie R., Vanhatalo, Anni, Lansley, Katherine E., DiMenna, Fred J., Wilkerson, Daryl P., Campbell, Iain T., Jones, Andrew M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 31.01.2011
• Subjects: Acetylcysteine - administration & dosage; Adult; Analysis of Variance; Antioxidant; Biomechanical Phenomena; Exercise Test; Exercise Tolerance - drug effects; Fatigue; Free Radical Scavengers - administration & dosage; Humans; Male; Medical Education; Nitric Oxide - blood; Oxidative metabolism; Oxygen Consumption - drug effects; Plasma nitrite; Plasma Volume - drug effects; Plasma Volume - physiology; Pulmonary Gas Exchange - physiology; Pulmonary Ventilation - drug effects; Pulmonary Ventilation - physiology; Pulmonary/Respiratory; Thiols; Time Factors; Young Adult; Fatigue; Thiols; Antioxidant; Oxidative metabolism; Plasma nitrite
• ISSN: 1569-9048; 1878-1519; 1878-1519
• DOI: 10.1016/j.resp.2010.10.002

We investigated the influence of the antioxidant N-acetylcysteine (NAC) on plasma nitrite concentration ([NO2−]), pulmonary oxygen uptake (V˙O2) kinetics and exercise tolerance. Eight males completed ‘step’ moderate- and severe-intensity cycle exercise tests following infusion of either NAC (125mgkg−1h−1 for 15min followed by 25mgkg−1h−1 until the termination of exercise) or Placebo (PLA; saline). Following the initial loading phase, NAC infusion elevated plasma free sulfhydryl groups compared to placebo (PLA: 4±2 vs. NAC: 13±3μMg−1; P<0.05) and this elevation was preserved throughout the protocol. The administration of NAC did not significantly influence plasma [NO2−] or V˙O2 kinetics during either moderate- or severe-intensity exercise. Although NAC did not significantly alter severe-intensity exercise tolerance at the group mean level (PLA: 776±181 vs. NAC: 878±284s; P>0.05), there was appreciable inter-subject variability in the response: four subjects had small reductions in exercise tolerance with NAC compared to PLA (−4%, −8%, −11%, and −14%) while the other four showed substantial improvements (+24%, +24%, +40%, and +69%). The results suggest that exercise-induced redox perturbations may contribute to fatigue development in recreationally-active adults.