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Departments of
1
Pharmaceutical Sciences and
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Hematology-Oncology, St. Jude Childrens Research Hospital, Memphis, TN 38105
3
College of Pharmacy and Medicine, University of Tennessee, Memphis, TN 38163
aAddress correspondence to this author at: Department of Pharmaceutical Sciences, St. Jude Childrens Research Hospital, 332 North Lauderdale, Memphis, TN 38105. Fax 901-525-6869; e-mail mary.relling{at}stjude.org.
Background: Mercaptopurine is a prodrug requiring intracellular activation to thiopurine nucleotides to exert antileukemic effect. We developed a reversed-phase liquid chromatographic assay for the quantification of mercaptopurine, thioguanine, and methylmercaptopurine nucleoside and nucleotide concentrations in the target tissue, the leukemic lymphoblast.
Methods: Leukemic blasts were isolated from peripheral blood and bone marrow by a standard Ficoll-hypaque procedure. Proteins were removed by ultrafiltration in the presence of dithiothreitol. Thiopurine ribonucleotides were converted into their respective ribonucleosides by treatment of ultrafiltrate with acid phosphatase. Thiopurine nucleosides and bases were measured by direct injection of ultrafiltrate into the chromatographic system. Thiopurine nucleotide concentrations were calculated by subtracting the thiopurine nucleoside concentrations measured after treatment with acid phosphatase from those measured after direct injection of ultrafiltrate in the chromatographic system. Analytes were separated on a C18 Supelco column with ammonium phosphate-methanol eluent coupled with ultraviolet detection.
Results: CVs for intra- and interday precision were 1.114% (median, 4.9%), and recovery of added analyte was 89126% (median, 105%) at low and high concentrations of analytes, except for mercaptopurine riboside. The median signal for each of the five metabolites in lymphoblast samples was 98% (range, 80106%) of that in water. Detection limits for thiopurine bases and nucleosides ranged from 0.5 to 4.5 pmol/5 x 106 cells.
Conclusions: This method is suitable for measurement of thiopurine metabolite concentrations in lymphoblasts in children with acute lymphoblastic leukemia following a single dose of intravenous mercaptopurine.
The following articles in journals at HighWire Press have cited this article:
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S. Hoover and R. Striker Thiopurines inhibit bovine viral diarrhea virus production in a thiopurine methyltransferase-dependent manner J. Gen. Virol., April 1, 2008; 89(4): 1000 - 1009. [Abstract] [Full Text] [PDF] |
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G. Zaza, M. Cheok, W. Yang, J. C. Panetta, C.-H. Pui, M. V. Relling, and W. E. Evans Gene expression and thioguanine nucleotide disposition in acute lymphoblastic leukemia after in vivo mercaptopurine treatment Blood, September 1, 2005; 106(5): 1778 - 1785. [Abstract] [Full Text] [PDF] |
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M. Shipkova, V. W. Armstrong, E. Wieland, and M. Oellerich Differences in Nucleotide Hydrolysis Contribute to the Differences between Erythrocyte 6-Thioguanine Nucleotide Concentrations Determined by Two Widely Used Methods Clin. Chem., February 1, 2003; 49(2): 260 - 268. [Abstract] [Full Text] [PDF] |
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