Mineral fiber-induced leukocyte activation: the role of intra- and extracellular calcium.

ABSTRACT

The role of intra- and extracellular calcium in the activation of human polymorphonuclear leukocytes (PMNL) to produce reactive oxygen metabolites (ROM) were studied by using soluble, formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate (PMA), or particulate stimuli, quartz or chrysotile. A calcium channel inhibitor, verapamil, attenuated only quartz-induced elevation of free intracellular calcium ([Ca2+]i) and ROM production. Likewise, ethyleneglycol-bis (aminoethyl ether) tetraacetic acid (EGTA) attenuated quartz-, chrysotile- and fMLP-induced elevation of [Ca2+]i and ROM production. It also inhibited PMA-induced ROM production. A calcium ionophore, A23187 amplified ROM production by all of these stimuli. These results suggest that both intra- and extra-cellular calcium are required for the full activation of respiratory burst by soluble and particulate stimuli in human PMNL.