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Modulation of contractile apparatus Ca2+ sensitivity and disruption of excitation–contraction coupling by S‐nitrosoglutathione in rat muscle fibres

Non‐technical summary  Repeated activity of muscle fibres generates reactive oxygen species (ROS), and these may affect many intracellular processes, possibly modifying force production both in the short‐term and the long‐term. ROS applied to muscle fibres can cause increased or decreased force responses, but the mechanisms and sites involved are not well understood. In the experiments here, the surface membrane was removed from individual muscle fibres and various ROS applied. In this way it was possible to determine the effects on each of the steps involved in muscle contraction. The various ROS were found to affect force responses primarily by increasing or decreasing the sensitivity of the contractile proteins to calcium ions. The ROS did not appreciably affect electrical excitability, calcium release from the internal stores or the maximum force producing capacity of the contractile proteins unless applied at very high concentration for a prolonged period. Interestingly, one particular ROS known to be generated inside muscle fibres did disrupt signalling and contraction, and this might account for the ability of ROS to cause long‐lasting muscle fatigue in certain circumstances.