A cytosolic calcium transient is not necessary for degranulation or oxidative burst in immune complex-stimulated neutrophils

Receptor-mediated activation of neutrophils (PMN) initiates possibly interdependent events, including a rapid transient increase in [Ca2+]i, implicated as a second messenger. To investigate whether this transient is required for eventual degranulation, PMN were incubated with an intracellular Ca2+ chelator (BAPTA), then exposed to chemotactic peptide [N-formyl-methionyl-leucyl-phenylalanine (fMLP)l with or without cytochalasin B (CB) or to high-valency immune complexes (HIC); delta[Ca2+]i, delta(pH)i, oxidative burst, and elastase release were then evaluated (plus or minus EGTA 15 s before stimulation) after 2 and 15 min incubation in 0.9 mM Ca2+. With either fMLP plus CB or HIC stimulation, BAPTA-treated cells were unable to achieve a Ca2+ transient with a 2-min incubation, whereas a 15-min incubation allowed the BAPTA-treated cells to recover a portion of the delta[Ca2+]i. Even though BAPTA-treated cells were unable to mount a delta[Ca2+]i at 2 min, HIC-stimulated BAPTA-treated cells were able to elicit an oxidative burst (33% of control) and degranulation (67% of control). Therefore, we conclude that delta[Ca2+]i modulates but is not required for oxidative burst or degranulation.