Breter HJ, Maidhof A, Zahn RK. The quantitative determination of metabolites of 6-mercaptopurine in biological materials. III. The determination of 14C-labeled 6-thiopurines in L5178Y cell extracts using high-pressure liquid cation-exchange chromatography.
BIOCHIMICA ET BIOPHYSICA ACTA 1978;
518:205-15. [PMID:
418811 DOI:
10.1016/0005-2787(78)90178-8]
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Abstract
A method is presented for the separation of 6-thiopurine bases and ribonucleosides, of sulphate anions and of common purine bases and oxidized purines by means of high-pressure liquid cation-exchange chromatography using a 0.18 X 100 cm column, filled with Beckman M71 resin, and eluted with 0.4M ammonium formate, pH 4.6, at a linear flow velocity of 5.2 cm/min at 50 degrees C. The method has been applied to the separation and quantitative determination of 14C-labeled 6-mercaptopurine metabolites in HClO4 extracts of L5178Y murine lymphoma cells. Distribution patterns of 14C radioactivity within the cells after a 24 h incubation period with (8-14C)-labeled 6-mercaptopurine have been established. The indentification of 6-mercaptopurine metabolites, such as 6-thioxanthosine ribonucleotide, 6-thioinosinic acid, 6-thioguanylic acid, 6-methylthioinosinic acid, and 6-thiouric acid, after the digestion of the extracts with alkaline phosphatase has been confirmed using the behaviour of each compound in enzymatic peak-shifting analyses with purine nucleoside phosphorylase and the corresponding elution volumes of 6-thiopurine bases and ribonucleosides as proofs. According to the specific radioactivity of the (8-14C)-labeled 6-mercaptopurine batch, the amounts of the various 6-mercaptopurine metabolites in about 6% of the total HClO4 extract of 1.6 . 10(8) labeled cells have quantitatively been determined as 1--130 pmol. The intracellular concentration of 6-thiopurines was determined at 1.4 . 10(-5)mol/1.
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