Fluoride inhibition of protein and DNA synthesis in cells in vitro.

Fluoride concentrations at and above 0.9 mM caused a progressive, concentration-related inhibition in the incorporation of both 14C-leucine and 3H-thymidine in LS cells incubated in medium with serum. The incorporation of leucine was more affected than that of thymidine. Lowering the pH enhanced the effect of fluoride on both. Removing serum from the incubation medium changed the effect of fluoride, particularly at low pH (7.0). Incorporation of leucine was then stimulated by low fluoride concentrations (0.5 and 0.9 mM), and the effect on thymidine incorporation was eradicated up to 1.3 mM-NaF. No differences were found in the pool and the specific activity of 14C-leucine in the fluoride exposed cells compared to control cells without fluoride (incubated at pH 7.4 in medium without serum). The cellular pool of 3H-thymidine decreased markedly during the incubation period, somewhat less in the fluoride exposed cells than in the control.