Mutagenicity of 2-amino-N6-hydroxyadenine to TK6 human lymphoblast cells

TK6 human lymphoblast cells (tk +/-; hprt+) were treated with various concentrations of 2-amino-N6-hydroxyadenine (AHA) for 24 h. AHA was quite toxic to TK6 cells in the dose range 0-0.05 micrograms/ml, but additional toxicity was not observed between 0.05 and 0.10 micrograms/ml. AHA induced mutations at 2 distinct genetic loci: the autosomal thymidine kinase (tk) and the X-linked hypoxanthine-guanine phosphoribosyl transferase (hprt). Significant levels of both tk-NG mutants (normal growth rate of 16-18 h, colonies visible after 10-11 days incubation) and tk-SG mutants (slow growth rate of greater than 24 h, colonies visible after 18 days incubation) were induced. 15 hprt- mutants were isolated and analyzed by Southern blot. 8 of these had normal restriction fragment patterns after digestion with PstI, EcoRI, and HindIII, and were defined as 'point' mutations; the remaining 7 had partial deletions of the hprt gene. 32 tk- mutants were also isolated. 3 of 22 normal growth mutants and 6 of 10 slow growth mutants had lost the active tk allele. These data suggest that both point mutations and larger-scale alterations are induced by AHA.