The genotoxic and cytotoxic activities of inorganic fluoride in cultured rat bone marrow cells.

The effects of sodium and potassium fluoride (NaF and KF) at concentrations ranging from 10(-7) to 10(-2) M for 12, 24, or 36 h on cultured rat bone marrow cells have been studied with respect to cytotoxicity and induction of sister-chromatid exchanges (SCE). At the three exposure times, cell survival progressively decreased with increasing concentrations. Treatment with 10(-2) M fluoride resulted in a statistically significant death (62-65%) of cells. Similarly, no dividing cells were encountered at concentrations of 10(-3) M and 10(-2) M, and significant reductions in mitotic index (MI) were calculated at 10(-4) M. In contrast, cell kinetics, expressed as cell proliferation index (CPI), revealed no significant inhibitory effect of fluoride on cell proliferation. Furthermore, the mean SCE score reached a maximum (7.64 SCE/cell) in the 24-h-treated cultures. This value was not significantly different from that observed in sodium chloride (NaCl) at 10(-2) M (5.42 SCE/cell) and distilled water (4.86 SCE/cell) controls. In comparison, mitomycin-C (MMC, positive control) at 5 x 10(-8) M caused an average of 22.13 SCE/cell. These results indicated an inhibition of cell division and death of cells with high doses of fluoride with no effect on SCE frequencies.