title: High-performance liquid chromatographic assay of methylthioguanine nucleotide.
abstract: This paper describes a specific and sensitive reversed-phase HPLC assay for the measurement of 6-methylthioguanine (methyl-TG) and methyl-TG nucleotides (methyl-TGNs) in red blood cells (RBCs), which is suitable for routine clinical use. Briefly, an ethyl acetate extract of RBCs is evaporated and reconstituted in 0.1 M HCl. The methyl-TG is separated from other thiopurines by reversed-phase HPLC and quantitated using UV detection. For the measurement of methyl-TGNs the free base (methyl-TG) is obtained by acid hydrolysis of the nucleotide back to the parent thiopurine. The intra-assay C.V. over the concentration range of 0.055-1.10 nmol methyl-TG per 4x10(8) (100 microl) RBCs ranged from 2.8 to 8.5%, and the mean recovery of methyl-TG over the calibration range was 61.6% (coefficient of variation, C.V., 3.8%). The lower limit of reproducibility was 0.055 nmol extracted from 100 microl RBCs. Analysis of blood samples from children with leukaemia receiving 6TG chemotherapy, revealed RBC methyl-TGNs at concentrations ranging from 323 to 1365 pmol per 8x10(8) RBCs. No methyl-TG was detected in any of the patient samples.
authors.affiliation: The University of Sheffield Department of Medicine and Pharmacology, Royal Hallamshire Hospital, UK.
authors.forename: K
authors.initials: K
authors.lastname: Rowland
authors.forename: L
authors.initials: L
authors.lastname: Lennard
authors.forename: J S
authors.initials: JS
authors.lastname: Lilleyman
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000097:blood* / Q000627:therapeutic use; D002648:Child; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D015122:Mercaptopurine / Q000097:blood / Q000627:therapeutic use; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood / Q000188:drug therapy; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet; D013866:Thioguanine / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use
chemical_list: D000964:Antimetabolites, Antineoplastic; C035366:6-methylthioguanine; D015122:Mercaptopurine; D013866:Thioguanine