Chinese hamster cells (line CHO) were examined for cadmium-induced growth-rate perturbations and chromosomal aberrations. The threshold concentration of Cd++ for the induction of chromosomal aberrations in CHO cells cultured in F-10 medium supplemented with 15 newborn calf serum was determined to be 1 × 10–6 M. CHO cells grown in the presence of nontoxic levels of Cd+ + (2×10-7 m) for 12 wk became resistant to toxic levels (2 x 10–6 m) after this exposure. Metaphase cells in these resistant populations contained only background levels of chromosomal aberrations. CHO cells grown in medium supplemented with several types of serum (fetal calf, newborn calf, and human) at concentrations commonly used for in vitro culture (5–20 v/v) or found in mammalian circulatory systems (50 v/v) differed markedly in Cd+ + tolerance. Cells grown in medium containing 1 × 10–6 MCd++ and supplemented with human or newborn calf serum were slightly protected against Cd++ damage at high serum concentrations (30 and 50 v/v) and accumulated approximately 90 µg Cd++/109 cells in 48 h. Cells growing at low or high concentrations of fetal calf serum were completely protected from 1×10-6 m Cd++ and accumulated approximately 12 µg Cd/109 cells in 48 h. The threshold Cd++ concentration for euploid Chinese hamster cells derived from skin, lung, and kidney tissues was determined to be 2 x 10–δ m. Cadmium does not induce elevated sister chromatid exchange levels. These results demonstrate the necessity for standardized protocols for cytogenetic investigations of Cd++ toxicity and may help to explain the discrepancies between studies of chromosome damage in patients with high Cd++
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