Quantitative Mammalian Cell Mutagenesis and a Preliminary Study of the Mutagenic Potential of Metallic Compounds

Résumé du livre

We have defined a set of stringent conditions required to quantify specific gene mutation in a mammalian cell system, CHO/HGPRT. Greater than 98% of the 6-thioguanine (TG)-resistant variants were shown to be deficient in the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity in Chinese hamster ovary (CHO) cells. The sensitive and quantitative nature of this assay was utilized to study the structure-activity (mutagenicity) relationship of various classes of chemicals. Mutagenicity as determined in the CHO/HGPRT assay, appears to correlate well (76/83 (92%)) with the reported animal carcinogenicity of 108 chemicals studied. The system also appears to be suitable for studying the mutagenicity and cytotoxicity of metallic compounds. We found that cis-dichlorodiammine Pt(II) (cis-Pt(NH/sub 3/)/sub 2/Cl/sub 2/) (cis-DDP), one of the widely used inorganic antitumor agents, is cytotoxic and mutagenic. Mutagenicity of cis-DDP correlates with its binding to DNA. However, trans-DDP, (Pt(NH/sub 3/)/sub 4/)Cl/sub 2/, and K/sub 2/(PtCl/sub 4/) exhibit greatly reduced biological activities. Among 14 other metals studied, we found that carcinogenic metallic compounds, such as MnCl/sub 2/, NiCl/sub 2/, and BeSO/sub 4/ are mutagenic, while non-carcinogenic compounds such as MgCl/sub 2/ and H/sub 2/SeO/sub 3/ are not. Determination of metal mutagenicity is apparently complicated by the ionic composition of the medium. This may account in part for varying results in studies of the mutagenicity of other metallic compounds. Further refinement of the assay conditions, especially with respect to the ionic environment necessary for quantifying mutagenesis of each metallic agent, is in progress.