Metabolism of rat skeletal muscle after spinal cord transection

We investigated the energy metabolism of the gastrocnemius muscle of the rat after spinal cord transection, using in vivo (31)P magnetic resonance spectroscopy (MRS). Spectra were obtained at rest and during exercise and recovery before, and at different time-points after, spinal cord transection. At rest, the adenosine triphosphate (ATP) level was not altered and the intracellular pH became permanently more alkaline. In electrically stimulated muscle, cord transection caused a greater phosphocreatine depletion than in control animals, and the maximum rate of oxidative ATP synthesis was significantly diminished; at days 30 and 60 after transection, an intracellular acidification was observed at the end of exercise. These effects indicate that, as in humans, spinal cord transection in rats leads to a decrease in mitochondrial oxidative metabolism and probably to an increase in anaerobic metabolism. This experimental model may prove useful for evaluating various approaches to improve muscle function in paraplegia.