Plasma glutamate levels in normal subjects and in patients with amyotrophic lateral sclerosis.

Altered glutamate tolerance has been implicated in the aetiology of amyotrophic lateral sclerosis (ALS). Plaitakis & Caroscio [ 11 reported plasma fasting levels of 2 1.4 f 7.9 pnol/l in 22 control subjects and of 40.8 f 12.7 pmol/l in 22 patients with ALS. These workers also reported significantly greater elevation of plasma glutamate in patients after oral administration of monosodium glutamate (MSG). Previously. Patten et al. [2] reported no significant differences between the serum fasting concentration of 12 control subjects (49 f 19 pmol/l) and that of 12 patients (60 k 29 pmol/l). In both studies glutamate was determined by direct automated amino acid analysis. The discrepancies between these reports may have arisen from procedural differences in sample preparation. In the present study glutamate was determined in whole blood, plasma and erythrocytes by the enzymic method of Beutler [3] after deproteinization of the samples with perchloric acid. Glutamine was subsequently determined in all samples after treatment with glutaminase