Skeletal muscle metabolism in uremic rats: a 31P-magnetic resonance study

The effect of uremia on skeletal muscle metabolism of the rat was examined using 31P-magnetic resonance spectroscopy. Three weeks following either a 5/6 nephrectomy or a sham operation, Wistar rats were placed in a 7T magnet, and the sciatic nerve was stimulated for 10 min. Analysis of spectra allowed calculation of intracellular pH and the relative concentrations of phosphocreatine (PCr), inorganic phosphate (Pi) and ATP. [ADP] was calculated from the creatine kinase equilibrium. There was a significant reduction in the resting intracellular [Pi] despite an elevation in extracellular [Pi], probably due to a reduction in the activity of the membrane Na/Pi cotransporter on account of a reduced sodium gradient. Despite anemia and uremia, there were no significant metabolic abnormalities during exercise and recovery accompanying this substantial reduction in glomerular filtration rate implying that at this level of renal impairment, there is no mitochondrial dysfunction.