Effect of fluoride on movement of concanavalin A-acceptor molecules of human neutrophils.

The effects of fluoride (F) on neutrophil protuberance formation and induced Con A acceptor molecule migration were assessed microscopically. Below 5 mM, F had little effect on acceptor migration, while it markedly inhibited formation of colchicine-induced protuberances. The anion also increased the rate at which preformed protuberances regressed. Since protuberance formation is enhanced by disassembly of microtubules, these data suggest that F promotes and/or stabilizes microtubule assembly. Microtubule assembly is favored by binding of GTP to tubulin subunits, while GDP binding favors disassembly of microtubules. Since F binds with GDP, forming a new complex that mimics GTP, the anion would be expected to enhance microtubule assembly. Over the same F concentration range, the anion failed to inhibit acceptor polarization, but did inhibit cytochalasin B-enhanced dispersion of prepolarized Con A acceptors, implying that, at low concentrations, F also affected microfilament cycling. Concentrations of F in excess of 5 mM inhibited acceptor migration as well as protuberance formation. At 20 mM, the anion abolished both events, yet at this same concentration F induced neutrophil superoxide generation and degranulation, suggesting that acceptor migration is not a prerequisite for these two neutrophil effector activities.