Metabolite alterations in the genetically spastic mouse.

The concentration of soluble amino acids in the brains of homozygous spastic mice was measured. It was found that brain arginine levels were reduced by 35% and urea concentration was 50% higher in affected mice. The activity of the brain and liver enzymes for arginine synthesis were similar in spastics and in controls. However, in spastic mice the activity of brain arginase is elevated. This increased arginase activity accounts for the decreased arginine concentration in the mutant mice.