摘要：Impaired excitation - contraction coupling occurs in eccentric contraction (ECC) - induced damaged muscles. It has been suggested that sarcoplasmic reticulum (SR) is susceptible to damage in the overstretched regions possibly marking the basis of excitation - contraction coupling damage. Recent studies have shown that dietary nitrate supplementation enhances SR function in fast-twitch muscles. In this study, we aimed to investigate whether dietary nitrate supplementation can alleviate a decline in muscle contractile properties and SR function following ECC. To this end, force production, Ca 2+ uptake, Ca 2+ release, and Ca 2+ -ATPase activity of the SR were examined in rat fast-twitch muscles immediately following ECC for 200 repetitions. In comparison with contralateral resting muscles, nitrate supplementation for up to 3 days resulted in an obvious decline in force production. However, there were no differences in terms of force production between 6-day nitrate-treated and contralateral muscles. Similar to the observations regarding force production, the SR Ca 2+ release rate changed from an obvious decrease following the 0- and 3-day dietary nitrate supplementation to no difference following the 6-day nitrate supplementation. In contrast, ECC decreased the Ca 2+ -ATPase activity and Ca 2+ uptake rate, irrespective of the period of dietary nitrate supplementation. Overall, t hese results indicate that dietary nitrate supplementation can alleviate ECC-related decreases in force production mediated through inhibited reductions in the SR Ca 2+ release function.
