[Studies on enzyme activities relating to amino acid mobilization in biopsied muscles]

We evaluated glutamine synthetase (GS) and alanine aminotransferase (GPT) activities in biopsied muscle from 40 cases of various neuromuscular diseases. GS and GPT catalyze the synthesis of glutamine and alanine, respectively, from amino acids derived in part from the breakdown of muscle proteins. The subjects were 7 cases of muscular dystrophy; 1 Duchenne type (DMD), 3 limb-girdle type, 2 facioscapulohumeral type (FSH), 1 Fukuyama type (FCMD); and 1 myotonic dystrophy (MyD); 5 mitochondrial myopathies; 11 inflammatory myopathies including 6 polymyositis and 3 myopathy associated with collagen disease; 5 endocrinological myopathies including 2 periodic paralysis; and, 11 cases of neurogenic amyotrophies [4 amyotrophic lateral sclerosis (ALS), 4 spinal progressive muscular atrophy (SPMA) and 3 other types]. Control subjects were 8 patients with thigh operations. Biopsied muscle was homogenized and assayed for GS activity by the method of Smith et al.; GPT was assayed by commercial kit. Protein was assayed by the method of Lowry et al. Enzyme activities between mean -2SD and mean +2SD of controls were considered to be the normal range. GS activity in control subjects was 28.22 +/- 7.13 (mean +/- SD) nmol glutamine formed/mg protein/hr. Fifteen of 40 cases showed increased enzyme activity, including DMD and FCMD, the acute phase of polymyositis, and periodic paralysis. GPT activity in controls was 16.56 +/- 4.05 IU/mg protein. Sixteen of 40 patients showed increased enzyme activity: FCMD, FSH, MyD, inflammatory and endocrinological myopathy, and ALS. On the other hand, mitochondrial myopathy showed significantly decreased activity.(ABSTRACT TRUNCATED AT 250 WORDS)