ERGOMETER EXERCISE IN MYOADENYLATE DEAMINASE DEFICIENT PATIENTS

Three patients with primary myoadenylate deaminase deficiency were sub jected to exercise on a bicycle ergometer at 125 W for 30 minutes. Blo od samples prior to, during, and at the end of exercise were analyzed for lactate, ammonia, and hypoxanthine. In addition, urinary hypoxanth ine excretion was measured. In these patients the serum lactate level increased to concentrations between 7.9 and 9.0 mmol/l at the end of e xercise whereas the mean lactate level in nine control subjects at the end of exercise was 3.3 mmol/l (range 1.1-8.1 mmol/l). There was no d ifference to control subjects in the exercise-induced increase in plas ma levels of ammonia and hypoxanthine or in the increase in urinary hy poxanthine excretion. The findings support the hypothesis of a reduced substrate supply to the citric acid cycle in myoadenylate deaminase d eficiency. The normal formation of ammonia and hypoxanthine excludes a marked loss of adenine nucleotides in working muscles in these patien ts.