Hypoxanthine phosphoribosyl transferase assay of lead mutagenicity on keratinocytes

An improved hypoxanthine phosphoribosyl transferase (HPRT) assay system was used to investigate the genotoxicity in human and rat keratinocytes exposed to Pb2+ 0.1-100 mumol.ml-1 in vitro. Autoradiography was applied to determine the number of labeled cells/cm2 of culture with [3H]TdR and liquid scintillation spectrometry was used to determine the incorporation of [3H]TdR into DNA counting of 6-thioguanine (TG)-resistant cells. The ratio between the number of labeled cells in the Pb2+ treated group (T) and in the control group (C) was calculated. When the cells exposed to Pb2+ 6 mumol.L-1 for 4 h, the T/C ratios reached 1.75 (scintillation, S), and 2.07 (autoradiography, A) in human and 1.37 (S), and 1.77 (A) in rat cells. A positive relation existed between the concentration of Pb2+ and mutagenicity. Lead should be considered as a weak mutagen in human and rat keratinocytes.