Arginase and free amino acids in hyperargininemia: leukocyte arginine as a diagnostic parameter for heterozygotes.

Arginase activity and free amino acids were measured in plasma, erythrocytes and leukocytes of patients with hyperargininemia and in controls. There is no arginase activity in the leukocytes and erythrocytes of homozygous patients; in heterozygotes it is normal to low. The activity is 50 to 100 times higher in leukocytes than in erythrocytes. In controls as well as in patients and heterozygotes, the amino acid concentrations are higher in leukocytes than in plasma and erythrocytes. In addition to the increased arginine in the three blood compartments (the result of an arginase deficiency), there is also an obvious decrease of aspartic acid in the erythrocytes of the patients. The arginine concentration in leukocytes of heterozygotes is as high as in homozygotes and can therefore be used as a diagnostic parameter for heterozygotes.