title: Determination of the L-DOPA/L-tyrosine ratio in human plasma by high-performance liquid chromatography. Usefulness as a marker in metastatic malignant melanoma.
abstract: A first procedure was devised for determining 3,4-dihydroxyphenylalanine (L-DOPA) in human plasma by isocratic RP-HPLC coupled with electrochemical detection. A second procedure was devised for determining 3-hydroxyphenylalanine (L-tyrosine) in human plasma by isocratic RP-HPLC coupled with fluorescence detection. These methods were used to ascertain the L-DOPA/L-tyrosine ratio in plasma of patients with melanoma. Reference values were established by analysis of the L-DOPA/L-tyrosine ratio in the plasma of 35 normal healthy subjects. For 29 patients diagnosed as having melanoma without metastasis, the L-DOPA/L-tyrosine (11.96 x 10(-5) +/- 2.69 x 10(-5)) level was not significantly different from that of 35 normal controls (11.20 x 10(-5) +/- 2.92 x 10(-5)). However, this level was significantly increased (p < 0.05) in the plasma of 17 patients with developing metastasis (21.02 x 10(-5) +/- 4.68 x 10(-5)).
authors.affiliation: Laboratoire de Biochimie A et de Neurobiologie, Hôpital Saint Louis, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Letellier
authors.forename: J P
authors.initials: JP
authors.lastname: Garnier
authors.forename: J
authors.initials: J
authors.lastname: Spy
authors.forename: B
authors.initials: B
authors.lastname: Bousquet
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002940:Circadian Rhythm; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007980:Levodopa / Q000097:blood* / Q000737:chemistry; D016014:Linear Models; D008543:Melanins / Q000096:biosynthesis; D008545:Melanoma / Q000097:blood* / Q000175:diagnosis / Q000473:pathology; D015203:Reproducibility of Results; D012878:Skin Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000473:pathology; D013050:Spectrometry, Fluorescence; D014443:Tyrosine / Q000097:blood*
chemical_list: D014408:Biomarkers, Tumor; D008543:Melanins; D014443:Tyrosine; D007980:Levodopa