Free amino acids and related compounds in the blood and urine of patients with malignant melanoma.

The concentrations of 22 free amino acids in plasma from 12 normal subjects and 10 patients with malignant melanoma were determined by ion exchange chromatography. There were no statistically significant differences between the 2 groups. Twentyfour-hr urine specimens from 15 normal individuals and 13 patients with disseminated melanoma were analyzed for 32 free amino acids or related compounds. In contrast to the plasma findings there were some changes in the urinary excretion of several free amino acids by patients with advanced melanoma. However, the excretion of tyrosine and phenylalanine, the amino acids of direct interest in this study, remains normal. The most significant difference was observed in the excretion of 1-methyl histidine (P < 0.001), in which the average value of patients with melanoma was approximately one-fourth that of normal.