Ischaemia‐induced injury in glycogen‐depleted skeletal muscle. Selective vulnerability of FG‐fibres

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Abstract
The effect of preischaemic glycogen-depletion on the development of skeletal muscle injury was investigated in rats subjected to tourniquet hind-limb ischaemia. Glycogen depletion was performed by direct electrical stimulation of the extensor digitorum longus (EDL) muscle during ischaemic conditions. The metabolite load during the subsequent 2.5 h of ischaemia was modified by allowing, or not allowing, a short reperfusion period after termination of the electrical stimulation. The extent of injury was evaluated morphologically after 5 or 15 h of reperfusion, by the combination of an intravital dye exclusion test and a histochemical staining, demonstrating calcium-precipitates-Alizarin red S. Minimal damage was found in animals subjected to ischaemia without preceding glycogen depletion. In both groups of preischaemically glycogen-depleted animals, significant irreversible injury occurred. The injury was significantly less in animals in which a wash-out period was allowed after termination of stimulation. Fast-glycogenolytic fibres (FG) were most sensitive to the ischaemic insult during both experimental conditions, while slow-oxidative fibres (SO) were spared. Fast-oxidative-glycogenolytic fibres (FOG) showed an intermediate response. The injury seemed to be established after 5 h of reperfusion, indicating that cells react with an all-or-nothing response in the present model.