5-S-cysteinyldopa in the plasma of melanoma patients and the renal clearance of this amino acid.

5-S-cysteinyldopa has been demonstrated in the plasma of two patients with metastases of malignant melanoma and a high excretion rate of 5-S-cysteinyldopa in the urine. In one patient the plasma clearance of 5-S-cysteinyl dopa was 30 ml/min and in the other 69 ml/min. These clearance values were 43 and 45%, respectively, of the creatinine clearance in the two patients.