Abstract
In an in vivo genotoxicity investigation of the action of fluoride (F) on bone marrow cells, sodium fluoride (NaF) was administered through the drinking water of 2–3 month old Swiss albino mice for 30 days at lower (7.5, 15, and 30 mg/L) and higher concentrations (100 and 150 mg/L). Mitotic inhibition, chromosomal aberrations, and chromatid breaks were most pronounced in mice that received the relatively low dose of 15 mg NaF/L. The effects became obvious after the first week of treatment and were maximal after 3 months of sustained exposure. Chromosome aberrations induced by one month treatment with 15 mg NaF/L was significantly higher than those found with the 100 and 150 mg NaF/L concentrations. The total number of femur bone marrow cells remained unchanged in all the treatment groups except in the 150 mg NaF/L group, in which it declined significantly. F treatment did not elicit any change in the percentage of viable cells in the bone marrow. Depletion of S-phase fraction of bone marrow cells occurred in the mice receiving 150 mg NaF/ L for 30 days, whereas treatment with 15 mg NaF/L for 90 days elevated the sub-G1 fraction, suggesting inhibition of DNA synthesis and up-regulation of apoptosis, respectively. These results indicate that the action of F in vivo is actually more genotoxic at certain lower concentrations than at higher concentrations.