Nitric oxide dependent delay in post‐fatigue contractile recovery in isolated fast‐twitch muscle: The role of the S‐nitrosoglutathione reductase

Abstract

During fatiguing contractions, skeletal muscle fibers produce nitric oxide (NO) (and possibly S‐nitrosoglutathione (GSNO)) due to the activation of calcium‐calmodulin dependent NO‐synthases (NOS). Myofibers contain GSNO reductase (GSNOR), an enzyme that consumes GSNO, thereby controlling intracellular protein S‐nitrosylation. The present investigation tested the hypothesis that GSNOR scavenges the GSNO produced during repetitive contractions to protect contractile and calcium handling proteins from being S‐nitrosylated. To test this hypothesis, the effects of acute inhibition of GSNOR (GSNORi; SPL‐334, 10 μM) on contractility during and after fatiguing contractions in fast‐twitch muscle were examined. Extensor digitorum longus (EDL) muscles from both hindlimbs of mice (C57BL6/J; 8–9 weeks old) were dissected and placed in an experimental chamber for ex‐vivo isometric force measurements during electrical stimulation. For each mouse, one EDL was treated with the GSNORi, or L‐NMMA (L‐N‐monomethyl Arginine, a NOS inhibitor; 400 μM), or both, while the other EDL served as an untreated control. Muscles were repetitively stimulated at increasing frequencies until force was decreased to 30% of initial force. Contractile recovery from fatigue was determined at submaximal and maximal frequencies of stimulation for 120 min post‐fatigue. The treatment with either GSNORi or L‐NMMA did not change maximal or submaximal force development. Acute GSNORi incubation significantly decreased the force development during fatiguing contractions (~30% less force) compared to untreated muscles. During muscle recovery from fatigue in the untreated control muscle, force developed at low frequencies of stimulation was ~80% of pre‐fatigue values after 120 min of recovery. However, when GSNORi was present during fatigue and during recovery post‐fatigue, the force developed at submaximal and maximal frequencies of stimulation were both significantly impaired compared to control (to 55–70% of pre‐fatigue values after 120 min, P<0.05 vs control). The NO‐dependent effects of GSNORi incubation on post‐fatigue recovery were tested when L‐NMMA was present to block NO production. L‐NMMA completely abolished the delayed contractile recovery detected with GSNORi. These data suggest that fatiguing contractions increase NO production thereby enhancing the intracellular amounts of GSNO, which can negatively affect muscle recovery post‐fatigue when GSNOR is inhibited. These results indicate that GSNOR activity has an important role in protecting contractile function during stimulation patterns that lead to muscle fatigue.Support or Funding InformationNIH (AR069577), CNPq (Universal)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.