title: Antioxidant treatment with N-acetylcysteine regulates mammalian skeletal muscle Na+-K+-ATPase alpha gene expression during repeated contractions.
abstract: Exercise increases Na(+)-K(+) pump isoform gene expression and elevates muscle reactive oxygen species (ROS). We investigated whether enhanced ROS scavenging induced with the antioxidant N-acetylcysteine (NAC) blunted the increase in Na(+)-K(+) pump mRNA during repeated contractions in human and rat muscle. In experiment 1, well-trained subjects received saline or NAC intravenously prior to and during 45 min cycling. Vastus lateralis muscle biopsies were taken pre-infusion and following exercise. In experiment 2, isolated rat extensor digitorum longus muscles were pre-incubated without or with 10 mm NAC and then rested or stimulated electrically at 60 Hz for 90 s. After 3 h recovery, muscles were frozen. In both experiments, the muscles were analysed for Na(+)-K(+) pump alpha(1), alpha(2), alpha(3), beta(1), beta(2) and beta(3) mRNA. In experiment 1, exercise increased alpha(2) mRNA by 1.0-fold (P = 0.03), but alpha(2) mRNA was reduced by 0.40-fold with NAC (P = 0.03). Exercise increased alpha(3), beta(1) and beta(2) mRNA by 2.0- to 3.4-fold (P < 0.05), but these were not affected by NAC (P > 0.32). Neither exercise nor NAC altered alpha(1) or beta(3) mRNA (P > 0.31). In experiment 2, electrical stimulation increased alpha(1), alpha(2) and alpha(3) mRNA by 2.3- to 17.4-fold (P < 0.05), but these changes were abolished by NAC (P > 0.07). Electrical stimulation almost completely reduced beta(1) mRNA but only in the presence of NAC (P < 0.01). Neither electrical stimulation nor NAC altered beta(2) or beta(3) mRNA (P > 0.09). In conclusion, NAC attenuated the increase in Na(+)-K(+) pump alpha(2) mRNA with exercise in human muscle and all alpha isoforms with electrical stimulation in rat muscle. This indicates a regulatory role for ROS in Na(+)-K(+) pump alpha isoform mRNA in mammalian muscle during repeated contractions.
authors.affiliation: Muscle, Ions and Exercise Group, School of Human Movement, Recreation and Performance, Centre for Ageing, Rehabilitation, Exercise and Sport Sciense, Victoria University, PO Box 14428, MCMC, Melbourne, Victoria 8001, Australia.
authors.forename: K T
authors.initials: KT
authors.lastname: Murphy
authors.forename: I
authors.initials: I
authors.lastname: Medved
authors.forename: M J
authors.initials: MJ
authors.lastname: Brown
authors.forename: D
authors.initials: D
authors.lastname: Cameron-Smith
authors.forename: M J
authors.initials: MJ
authors.lastname: McKenna
mesh_terms: D000111:Acetylcysteine / Q000008:administration & dosage / Q000494:pharmacology*; D000328:Adult; D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004558:Electric Stimulation; D015444:Exercise; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D009119:Muscle Contraction; D020033:Protein Isoforms; D052097:Quadriceps Muscle / Q000187:drug effects* / Q000201:enzymology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D055815:Young Adult
chemical_list: D000975:Antioxidants; D020033:Protein Isoforms; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase; D000111:Acetylcysteine