Cultured human cells with a high content of metallothionein show resistance against gold-chloride.

Resistance to gold(III)chloride was tested in cultures of human epithelial cells derived from normal skin. Two cell strains were used, a 'wild type' (HE) and a substrain, previously made resistant to 100 mumol/l of CdCl2 (HE100), with a high content of the cysteine-rich cytoplasmic protein, metallothionein. Cell growth was studied for a period of 4 days during exposition to gold-chloride (100-400 mumol/l of HAuCl4 X 4H2O). Gold-chloride produced a dose-dependent inhibition of cell proliferation of both cell strains. Compared with untreated control cells, however, the percentage survival after 4 days' treatment with 400 mumol/l was only 11% of HE cells, vis-à-vis 44% of the HE100 cells. After 24 hours' exposition to 200 mumol gold-chloride/l, the subcellular distribution of gold was determined by gel-filtration of cytosols, and subsequent analyses for Au by flame atomic absorption spectrophotometry. In the HE100 cells 30% of the cytosolic gold co-eluted with the metallothionein. In the HE cells, which do not contain detectable amounts of metallothionein, only traces of gold were found in the corresponding eluate fractions. The total amount of intracellular gold was 15% higher in HE100 than in HE cells. This study renders it probable that the binding of gold to pre-existing metallothionein in HE100 cells affords protection against otherwise lethal gold concentrations. The significance of the results is briefly discussed in relation to therapeutic use of gold substances.