Pre-exercise nitric oxide donor supplementation attenuates decline in muscle contractile force and ryanodine receptor proteolysis following eccentric contraction

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The aim of this study was to elucidate the effects of oral administration of S-nitrosoglutathione (GSNO), a nitric oxide donor, on force production and Ca²⁺ regulatory proteins in fast-twitch muscles subjected to eccentric contraction (ECC). Rats were administered 1 mmol kg^-1 d^-1 GSNO for five days before ECC. Force production, sarcoplasmic reticulum (SR) Ca²⁺-ATPase activity, and amounts of Ca²⁺ regulatory proteins were examined after 200 ECC repetitions. Three days after ECC, the experimental extensor digitorum longus muscles and the contralateral resting muscles were quickly excised and used for the experiment. Force production at 20 Hz returned to resting levels in GSNO-treated muscles, but not in resting muscles. Western blot analysis showed that GSNO ingestion inhibited ECC-induced loss of ryanodine receptor (RyR) 1 responsible for SR Ca²⁺ release capacity. Overall, these findings indicate that oral administration of a nitric oxide donor prior to ECC can promote force recovery following ECC and suggest that this benefit may be due to inhibition of RyR proteolysis.