This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liliemark, J. Articles by Peterson, C. Search for Related Content PubMed Articles by Liliemark, J. Articles by Peterson, C.

On the Paradoxically Concentration-dependent Metabolism of 6-Mercaptopurine in WEHI-3b Murine Leukemia Cells¹

Department of Medicine, Karolinska Institute at Huddinge Hospital, S-141 86 Huddinge, and Department of Clinical Pharmacology, Karolinska Hospital, S-104 01 Stockholm, Sweden

The intracellular metabolism of 6-mercaptopurine (6-MP) was studied in a murine leukemia cell line, WEHI-3b. Cells were incubated 3 to 24 h with 10 nM to 50 µM 6-MP. Nucleotides were extracted with perchloric acid, and the 6-thiopurine nucleotides were isolated on mercurial cellulose. The endogenous ribonucleotides in the perchloric acid extracts as well as 6-thiopurine nucleotides were separated and quantified with anion exchange high-performance liquid chromatography. The concentration of 6-thioinosinate (6-TIMP) and 6-thioxantinate (6-TXMP) increased with an increasing 6-MP dose. The concentration of the 6-thioguanosine nucleotides (6-TGN) increased with 6-MP concentrations between 10 nM and 1 µM. However, further increase in 6-MP concentration led to a decrease in the formation of 6-TGN. At 50 µM 6-MP, the concentration of 6-thioguanosine 5'-triphosphate was one fifth of that seen at 1 µM. The incorporation of 6-[³⁵S]mercaptopurine into DNA was also slightly higher at 1 µM compared with 50 µM. The cytocidal effect on clonogenic cells was one log greater at 1 µM 6-MP compared with 50 µM 6-MP. The decrease of 6-TGN was accompanied not only by an increased 6-TIMP concentration but also by an inhibition of the purine de novo synthesis and consequently by a decrease of the cellular ATP concentration. The ATP concentration in the cells treated with 1 µM 6-MP could be reduced to the level seen in cells treated with 50 µM 6-MP by simultaneous incubation with 0.3 µM antimycin A. This decrease of ATP concentration was accompanied by a reduction of 6-TGN and to a lesser extent of 6-TXMP. These experiments suggest that the "self-limiting" phenomenon in the metabolism of 6-MP might be caused by a depletion of ATP by inhibition of purine de novo synthesis presumably by 6-TIMP.

¹ Supported by grants from the Swedish Cancer Society, the Cancer Society in Stockholm, the Swedish Medical Research Council (Project No. 08640), the Swedish Medical Society, and the Swedish Child Cancer Foundation.

² To whom requests for reprints should be addressed.

Received 5/24/89. Revised 9/25/89. Accepted 10/ 3/89.

This article has been cited by other articles:

				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]