The interaction of fluoride with rabbit polymorphonuclear leukocytes: Induction of exocytosis and cytolysis

Abstract

Pretreatment of rabbit polymorphonuclear leukocytes (PMN's) with sodium fluoride, followed by removal of extracellular fluoride and addition of calcium, results in strong exocytosis. This is shown by the selective release of granule-associated components such as lysozyme and β-glucuronidase. The degree of exocytosis is dependent on temperature and fluoride concentration during preincubation. This effect is characterized by a pH-dependent lag time. Removal of fluoride and addition of calcium to PMN's preincubated for a period shorter than the lag time does not result in exocytosis. Fluoride-dependent exocytosis is a rapid process, being complete after 3 min incubation with calcium, and is dependent on the calcium concentration. The penetrating sulfhydryl reagents cytochalasin A and N-naphtyl maleimide, and the glycolysis inhibitors 2-deoxyglucose and iodoacetate, inhibit fluoride-dependent exocytosis. Fluoride-dependent exocytosis did not occur in human peripheral PMN's in contrast to rabbit (peritoneal) PMN's. Exocytosis may be due either to an interaction of fluoride with the inner side of the membrane or to a reaction with a specific membrane component. Apparently thereby calcium is enabled to cross the membrane and to act intracellularly. When calcium and fluoride are simultaneously present in the medium either exocytosis or cytolysis may occur. The hemolytic action of calcium and fluoride on erythrocytes suggests that here cytolysis is due to an interaction of calcium fluoride crystals with the cell.