Purine metabolism in thioguanine-resistant glioma cells

6-Thioguanine resistant strains of rat glioma cells were selected spontaneously and after mutagen treatment. Both mutant lines exhibited a severe deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase, increased intracellular concentrations of 5-phosphoribosyl-1-pyrophosphate and rate of the early steps of purine biosynthesis, and an inability to incorporate guanine, but not adenine, into soluble purine nucleotides.