Résumé :
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Acute quadriplegic myopathy (AQM) is commonly observed in patients suffering from critical illness, and is notably characterized by an early severe limb muscle weakness. The basic mechanisms underlying such muscle weakness remain poorly understood. It may be related to various components, i.e., sepsis, prolonged mechanical ventilation, postsynaptic block of neuromuscular transmission (NMB), systemic corticosteroid hormone treatment (CS), and muscle unloading. The present study aimed at exploring the relative importance of each component on the early development of limb muscle weakness using a porcine model. 21 pigs were mechanically ventilated and exposed to various combinations of NMB, CS and/or endotoxin-induced sepsis, for a period of five days. Biopsy specimens from biceps femoris on day 1 and 5, allowed the measurements of muscle function (single muscle fiber preparation), protein (12% SDS-PAGE gels, ELISA assay) and mRNA (Real-time PCR) expressions. Results showed interesting findings pointing out the major components that seriously accounts for the early development of AQM. On day 5, single muscle cell force-generating capacity was dramatically altered, the severity was related to the exposition to the various components: combination of sepsis, CS and NMB > sepsis > CS > NMB. This impairment may be directly related to the lower expression of contractile proteins, related to degradation in the early phase of the disease.
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