Cell detachment and growth of fibroblasts as parameters for cytotoxicity of inorganic metal salts in vitro

Eight inorganic metal compounds (AlCl3, Al(OH)3 gel, Al(OH)3 salt, SnCl2, ZnSO4, K2Cr2O7, CdCl2, HgCl2) were tested for their cytotoxic effect on an established hamster fibroblast line (BHK-21/C13) in vitro using a cell detachment assay and two different growth assays, the cloning efficiency and the cell number after 2 days subconfluent culture as parameters. The test conditions for these assays were optimized, including incubation period, application of test substance, growth conditions and data analysis. Aluminum, zinc and tin compounds showed low cytotoxic effects when compared to potassium, cadmium and mercuric compounds. Potassium dichromate was highly toxic in both growth assays (0.0001-0.01 mM, with a clear dependency on the incubation time), whereas it proved to be only slightly toxic in the detachment assay (0.1-5 mM). Cadmium and mercuric chlorides were the most toxic compounds in the growth (0.00001-0.001 mM) and the cell detachment assays (0.01-0.1 mM). Variable incubation periods barely affected the cytotoxicity of mercuric chloride. Ranking of these cytotoxicity data was found to be identical to the ranking of LD50 values (oral, rat) as well as to the ranking according to threshold limit values for human workroom environment, and of human eye irritation data.