Untitled

Abstract

Recently it has been hypothesized that, in skeletal muscle, NO produced directly by high-frequency stimulation could produce contraction through reactions with thiol groups on the sarcoplasmic reticulum (SR). However, a possible cGMP-mediated relaxing effect, similar to that seen in smooth muscle, has also been demonstrated. We used purified SR preparations and single fibres from frog fast muscles incubated with different concentrations of sodium nitroprusside (SNP) in this study. The results obtained from a long low-frequency stimulation, together with those from a study on Ca2+ transport regulation, showed that the presence of NO precursor induced: an acceleration of the onset of fatigue in single fibres; a decreased vesicular Ca2+ content due to increased Ca2+ release; a shift to open status in SR Ca2+ channels; an increase in SR Ca2+ pump activity. The data presented in this paper seem to indicate that the increased NO in the muscle fibres can influence muscle activity in different ways, perhaps depending on the metabolic status of the muscle and target (filaments, sarcolemma, SR) with which the NO (or its derivatives) acts.

Relationship between Human Aging Muscle and Oxidative System Pathway

“…There are insights have correlated oxidative damage to the mechanisms underlying EC (excitation-contraction) coupling. Since Ca 2+ release channels are one of the major targets of oxidative damage [64, 65], the unbalance of Ca 2+ transport that is present in the sarcopenic muscle could be due to the modified oxidative status of those structures involved in Ca 2+ release and uptake [66]. Several studies have shown the presence of an enzyme, NAD(P)H-oxidase, that is associated with skeletal muscle SR (sarcoplasmic reticulum) [67].…”

Reactive Oxygen Species: Impact on Skeletal Muscle

“…Although it is not universally accepted (43, 56), several authors argue that interventions that increase cGMP signaling (e.g., NO donors, cGMP analogs, etc.) reduce skeletal muscle force production (1, 46, 221, 250, 251, 327). Similarly, contractile force can be increased by treatments that decrease cGMP levels (e.g.…”