Genotoxic effects of heavy metals in rat hepatocytes

Abstract

The genotoxic interaction of metals, which are common environmental contaminants, was studied in cultured hepatocytes. Freshly isolated rat hepatocytes were exposed to concentrations of cadmium, copper, silver and lead salts ranging from non-cytotoxic to moderately cytotoxic (as determined by LDH release), and the incorporation of [3H]thymidine into the DNA, as a measure of repair synthesis, was followed. In addition, the uptake of metals by the nuclear fraction was determined using Inductively Coupled Plasma/Mass Spectrometry or atomic absorption spectrophotometry. The evaluation of binding of 109Cd to the DNA in situ was also attempted. It was observed that after a 20 h exposure period, all the metals investigated were found in the nuclear fraction of hepatocytes, with Ag apparently being accumulated less efficiently. In parallel, Cd (0.18 to 1.8 microM) and Cu (7.9 to 78.5 microM) consistently produced a statistically significant stimulation of [3H]thymidine incorporation into the DNA, in the presence or absence of hydroxyurea while Ag was active only at the highest concentration tested (18.5 microM). In contrast, Pb failed to induce a UDS response at the levels used. Moreover, exposure of hepatocytes to 1.8 microM 109CdCl2 for 20 h led to a DNA binding ratio of 0.98 +/- 0.23 ng Cd/micrograms DNA. The present results support the view that the nucleus may be an important target organelle for metal toxicity.

In vitro embryotoxicity testing of metals for dental use by differentiation of embryonic stem cell test

“…Wang and Li (1998) reported that with the Ames test using salmonella, titanium and silver exhibited no mutagenicity. Denizeau and Marion (1998) used labeled thymidine to monitor DNA repair in rat hepatocytes and found that silver exhibited little genotoxicity unlike lead and the other metals studied. We subsequently found that silver and cobalt ions severely affect the IC 50 of both cells.…”

Induction of Micronuclei in Mice Bone Marrow Cells by Cobalt and Copper Chlorides

“…Previous studies have also demonstrated that copper have mutagenic and genotoxic activities in different biological test systems [6,12,18,30,36,43,47,49,51,55]. Furthermore, many earlier authors [32,35,37,45,48,50,52,54] have adversely observed toxicity of copper against different test organisms.…”

Lack of genotoxicity of silver iodide in the SCE assay in vitro, in vivo, and in the Ames/microsome test

“…Although hazards to humans from environmental pollution by heavy metals are already known, such effects by silver just recently have been investigated upon rat [5,6] and human [7] cells. Since the highly insoluble silver iodide, compared with silver, would exhibit a rather lower acute and/or chronic toxicity, for the purpose of the present study genotoxicity tests with increased sensitivity must be employed.…”