INTRACELLULAR PATTERN OF CYTOSOLIC CA2+ CHANGES DURING ADHESION AND MULTIPLE PHAGOCYTOSIS IN HUMAN NEUTROPHILS - DYNAMICS OF INTRACELLULAR CA2+ STORES

The subcellular pattern of cytosolic free Ca2+ ([Ca2+](i)) changes in human polymorphonuclear neutrophils (PMNs) was studied using imaging of fura-2 fluorescence (time resolution 12.5 ratios/s) to determine whether PMNs could obtain directional information from the [Ca2+](i) signal. [Ca2+](i) changes were observed during initial adherence, the subsequent chemotactic movement, and the phagocytosis of opsonized yeast particles. Initial adherence was followed by a rapid increase in [Ca2+](i) (from 90 +/- 10 to 290 +/- 40 nmol/L in 6.5 +/- 2.5 seconds; +/- SEM, n = 10), apparently homogeneously distributed over the entire cytoplasm, which preceded the spreading of the PMNs. [Ca2+](i) increases after the contact of the PMNs with yeast particles were of lower mean amplitude; [Ca2+](i) increased simultaneously throughout the cytosol. In the absence of extracellular Ca2+, multiple phagocytotic events could proceed normally without a mandatory [Ca2+](i) transient. In PMNs polarized on phagocytosis, gradients in [Ca2+](i) could be observed, [Ca2+](i) was more elevated in the periphagosomal area than in the remaining parts. Taken together, these data show that [Ca2+](i) waves do not provide the neutrophil with directional information during chemotaxis and phagocytosis. Sustained small inhomogeneity of [Ca2+](i) levels are consistent with a proposed redistribution of releasable Ca2+ stares on phagocytosis. (C) 1995 by The American Society of Hematology.