Permalink : http://hdl.handle.net/2115/90490

Fluoride (F) has been widely applied for the prevention of dental caries, but the range of application is limited because of acute toxicity. Moreover, the detailed toxicity mechanism is unclear. In this study, we consider that Na,K-ATPase from a rat brain is the target of acute toxicity of F, and we investigate the effects of F on Na,K-ATPase activities and the amount of phosphorylated intermediate (EP). F inhibited Na,K-ATPase activity, Na-ATPase activity, and K-pNPPase activity depending on the concentrations investigated. It was also found that aluminum (Al) increased the inhibition of ATPase activity by fluoride depending on the Al concentration and the optimum concentration was 100 μM Al. Activities were recovered to some extent by dilution, but not in the presence of both F and Al. This Al action required Mg2+, and the effect of Mg2+ could be replaced with Mn2+ or Ca2+. The amount of EP decreased depending on F concentrations investigated and Al further enhanced the inhibit ion of EP formation. However, while the activity was inhibited almost completely, about half of the EP formation remained. Deferoxamine decreased the effect of Al. These results suggest the following. F inhibited Na,K-ATPase activity by decreasing EP formation depending on its concentration, and Al increased the affinity of F for Na,K-ATPase. There are two inhibition mechanisms by F; inhibition of Na,K-ATPase activity by F alone is reversible, but the inhibition in the presence of F, Al, and divalent metals is irreversible.