31-P NMR CHARACTERIZATION OF THE METABOLIC ANOMALIES ASSOCIATED WITH THE LACK OF GLYCOGEN-PHOSPHORYLASE ACTIVITY IN HUMAN FOREARM MUSCLE

Exercise-induced changes in phosphorus-containing metabolites and intracellular pH (pHi) have been studied in the finger flexor muscles of 3 patients with glycogen phosphorylase deficiency (McArdle's disease) in comparison to 14 healthy volunteers. At rest, no difference was observed for PCr/Pi ratio and pHi while patients exhibited a higher PCr/ATP ratio (5.91 ± 0.98 vs 4.02 ± 0.6). At end-of-exercise, PCr/Pi was abnormally low (0.51 ± 0.19 vs 1.64 ± 0.37) whereas no acidosis was observed. The slow recovery of PCr/Pi ratio indicates an impairment of oxidative capacity accompanying the defect in the glycogenolytic pathway. The failure to observe a transient Pi disappearance at the onset of recovery (an index of glycogen phosphorylase activity) can be used in conjunction with the lack of exercise acidosis as a diagnostic index of McArdle's disease. © 1992 Academic Press, Inc.