Cell culture density dependent toxicity and chromatin changes upon cadmium treatment in murine pre-B-cells

Murine pre-B-cells grown in the presence of lower (1 microM) or higher (5 microM) concentration of cadmium chloride were separated into 13 fractions by centrifugal elutriation. The rate of DNA synthesis after cadmium treatment determined in permeable cells was dependent on cell culture density during cadmium treatment. Cell cycle analysis revealed a shift in the profile of DNA synthesis from replicative to repair DNA synthesis upon cadmium treatment. The study of the relationship between cell culture density and cell diameter at lower and higher cell densities in the presence of 1 microM cadmium chloride concentration showed that a. at 5 x 10(5) cell/ml or lower densities cells were shrinking indicating apoptotic changes, b. at higher cell culture densities the average cell size increased, c. the treatment of cells with low CdCl(2) concentration (1 microM) at higher cell culture density (>5 x 10(5) cell/ml) did not change significantly the average cell diameter. At 5 microM cadmium concentration and higher cell culture densities (>5 x 10(5) cell/ml) the average cell size decreased in each elutriated fraction. Most significant inhibition of cell growth took place in early S phase (2.0-2.5 C value). Apoptotic chromatin changes in chromatin structure after cadmium treatment were seen as large extensive disruptions, holes in the nuclear membrane and stickiness of incompletely folded chromosomes.