title: Assay of 6-thioguanine nucleotide, a major metabolite of azathioprine, 6-mercaptopurine and 6-thioguanine, in human red blood cells.
abstract: An assay for 6-thioguanine (6-TG) nucleotide, a major metabolite of the cytotoxic drugs azathioprine, 6-mercaptopurine and 6-thioguanine in human red blood cells (RBCs) has been developed. The metabolite was not detected in RBCs when azathioprine or 6-mercaptopurine was incubated with whole blood in-vitro. The assay for intracellular 6-TG nucleotide is specific and requires 8 X 10(8) RBCs (100 microliters packed cells) for which the limit of sensitivity is 30 pmole 6-TG nucleotide. Pre-dose blood samples were obtained, 12 h after the last azathioprine dose, from 10 renal transplant recipients with stable functioning cadaver grafts on a total daily dose of 150 mg azathioprine. The mean 6-TG nucleotide concentration was 171 pmole/8 X 10(8) RBCs (s.d. = 84). The assay is also suitable for use in measuring 6-TG nucleotide in the RBCs of leukaemic children undergoing 6-mercaptopurine treatment.
mesh_terms: D001379:Azathioprine / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007945:Leukemia, Lymphoid / Q000097:blood; D015122:Mercaptopurine / Q000378:metabolism* / Q000627:therapeutic use; D013866:Thioguanine / Q000378:metabolism*; D013873:Thionucleotides / Q000097:blood*
chemical_list: D006150:Guanine Nucleotides; D013873:Thionucleotides; C003964:6-thioguanylic acid; D015122:Mercaptopurine; D013866:Thioguanine; D001379:Azathioprine