Fluoride-mediated activation of guinea pig neutrophils

In guinea pig periotoneal neutrophils NaF at a concentration of above 5 mM elicited a dose-dependent, delayed and sustained activation of NADPH oxidase. Unlike in human neutrophils, in guinea pig cells, this response was independent of extracellular calcium. Fura2 fluorescence measurements indicated also a fluoride-mediated moderate elevation in the level of cytosolic calcium concentration. Pretreatment of neutrophils with pertussis toxin, blocked fluoride-promoted activation of NADPH oxidase, indicating that NaF stimulation was mediated by a G protein which is a pertussis toxin substrate. NaF-elicited calcium elevation was insensitive to the toxin. Upon transfer of NaF-stimulated cells to a fluoride-free medium, superoxide release declined and calcium levels diminished. The response of the deactivated, fluoride-prestimulated guinea pig neutrophils to a secondary stimulation with phorbol myristate acetate (PMA) or fMet-Leu-Phe, was either unaffected by the previous challenge with NaF (PMA) or augmented by it (the chemotactic peptide). In parallel to the activation of NADPH oxidase, NaF also induced translocation of protein kinase C to cell membranes. This effect was also abolished by a pretreatment with pertussis toxin.