Abstract
Abstract Among the pyrazolopyrimidine derivatives used in hyperuricemia, thiopurinol [4-mercaptopyrazolo-(3,4-d) pyrimidine] exhibits different therapeutic effects than those of allopurinol [4-hydroxypyrazolo-(3,4-d) pyrimidine] and oxypurinol [4,6-dihydroxypyrazolo-(3,4-d) pyrimidine] which leads us to assume that its hypouricemic mechanism is different. The action of the three derivatives has been compared: (a) as xanthine oxydase inhibitors: thiopurinol activity is intermediate between that of the two others, (b) as subtrates of the phosphoribosyl transferase system: the nucleotide of thiopurinol has been isolated and identified, (c) as natural substrate HGPRT inhibitors (guanine and hypoxanthine). Finally, their action on PRPP consumption and on its intracellular level has been specified. In the absence of precise data on the concentrations realized in vivo with the therapeutic doses used, the interpretation of enzymatic kinetic data does not appear significant. It seems, however, that allopurinol and thiopurinol reduce de novo synthesis of purine ribonucleotides by depressing the PRPP intracellular level.
Published Version
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