NDLI: N-acetylcysteine attenuates the decline in muscle Na+,K+-pump activity and delays fatigue during prolonged exercise in humans

Content Provider	PubMed Central
Author	Mckenna, Michael J. Medved, Ivan Goodman, Craig A. Brown, Malcolm J. Bjorksten, Andrew R. Murphy, Kate T. Petersen, Aaron C. Sostaric, Simon Gong, Xiaofei
Copyright Year	2006
Abstract	Reactive oxygen species (ROS) have been linked with both depressed Na+,K+-pump activity and skeletal muscle fatigue. This study investigated N-acetylcysteine (NAC) effects on muscle Na+,K+-pump activity and potassium (K+) regulation during prolonged, submaximal endurance exercise. Eight well-trained subjects participated in a double-blind, randomised, crossover design, receiving either NAC or saline (CON) intravenous infusion at 125 mg kg−1 h−1 for 15 min, then 25 mg kg−1 h−1 for 20 min prior to and throughout exercise. Subjects cycled for 45 min at 71% V˙O2peak, then continued at 92% V˙O2peak until fatigue. Vastus lateralis muscle biopsies were taken before exercise, at 45 min and fatigue and analysed for maximal in vitro Na+,K+-pump activity (K+-stimulated 3-O-methyfluorescein phosphatase; 3-O-MFPase). Arterialized venous blood was sampled throughout exercise and analysed for plasma K+ and other electrolytes. Time to fatigue at 92% V˙O2peak was reproducible in preliminary trials (c.v. 5.6 ± 0.6%) and was prolonged with NAC by 23.8 ± 8.3% (NAC 6.3 ± 0.5 versus CON 5.2 ± 0.6 min, P < 0.05). Maximal 3-O-MFPase activity decreased from rest by 21.6 ± 2.8% at 45 min and by 23.9 ± 2.3% at fatigue (P < 0.05). NAC attenuated the percentage decline in maximal 3-O-MFPase activity (%Δactivity) at 45 min (P < 0.05) but not at fatigue. When expressed relative to work done, the %Δactivity-to-work ratio was attenuated by NAC at 45 min and fatigue (P < 0.005). The rise in plasma [K+] during exercise and the Δ[K+]-to-work ratio at fatigue were attenuated by NAC (P < 0.05). These results confirm that the antioxidant NAC attenuates muscle fatigue, in part via improved K+ regulation, and point to a role for ROS in muscle fatigue.
Related Links	http://dx.doi.org/10.1113/jphysiol.2006.115352
Ending Page	288
Page Count	10
Starting Page	279
File Format	PDF
ISSN	00223751
e-ISSN	14697793
Journal	The Journal of Physiology
Issue Number	Pt 1
Volume Number	576
Language	English
Publisher	Blackwell Science Inc
Publisher Date	2006-10-01
Access Restriction	Open
Rights Holder	Blackwell Science Inc
Subject Keyword	Physiology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Physiology Sports Science

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