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1 The University of Melbourne
2 Victoria University
3 University of Western Australia
4 La Trobe University
* To whom correspondence should be addressed. E-mail: goodmanc{at}unimelb.edu.au.
Recent studies report that depletion and repletion of muscle taurine (Tau) to endogenous levels affects skeletal muscle contractility in vitro. In this study, muscle Tau content was raised above endogenous levels by supplementing male Sprague Dawley rats with 2.5% (w/v) Tau in drinking water for 2 weeks after which EDL muscles examined for in vitro contractile properties, fatigue resistance and recovery from fatigue after two different high frequency stimulation bouts was examined. Tau supplementation increased muscle Tau content by ~40%, isometric twitch force by 19%, shifted the force-frequency relationship upwards and to the left, increased specific force by 4.2% and and increased muscle calsequestrin protein content by 49%. Force at the end of a 10 s (100Hz) continuous tetanic stimulation was 6% greater than controls, while force at the end of the 3 min intermittent high frequency stimulation bout was significantly higher than controls with a 12% greater area under the force curve. For 1 h after the 10 s continuous stimulation, tetanic force in Tau supplemented muscles remained relatively stable while control muscle force gradually deteriorated. After the 3 min intermittent bout, tetanic force continued to slowly recovery over the next 1 h while control muscle force again began to decline. Tau supplementation attenuated F2-isoprostane production (a sensitive indicator of reactive oxygen species-induced lipid peroxidation) during the 3 min intermittent stimulation bout. Finally, Tau transporter protein expression was not altered by the Tau supplementation. Our results demonstrate that raising Tau content above endogenous levels increases twitch, sub-tetanic and specific force in rat fast twitch skeletal muscle. Also, we demonstrate that raising Tau protects muscle function during high frequency in vitro stimulation and the ensuing recovery period, and helps reduce oxidative stress during prolonged stimulation.
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