Activation of human neutrophils with chemotactic peptide, opsonized zymosan and the calcium ionophore A23187, but not with a phorbol ester, is accompanied by efflux and store-operated influx of calcium.
The objective of this study was to monitor alterations in cellular Ca2+ metabolism following activation of neutrophils with receptor- (chemotactic peptide, FMLP, 1 microM; opsonized zymosan, OZ, 0.5 mg/ml) and non-receptor (calcium ionophore, A23187, 1 microM; phorbol 12-myristate 13-acetate, PMA, 25 ng/ml)-mediated stimuli of the pro-inflammatory functions of these cells. Ca2+ fluxes in activated neutrophils were measured using a fura-2-based spectrofluorimetric method in combination with radiometric (45Ca) procedures which facilitate distinction between net efflux and net influx of the cation. Exposure of neutrophils to receptor-mediated stimuli and to A23187 was associated with an abrupt increase in cytosolic Ca2+ coincident with a rapid efflux of the cation which terminated at around 30 s. In the case of FMLP and OZ, this was followed by a delayed (30-60 s), store-operated influx of Ca2+, which was complete at around 5 min after addition of the stimulus. With A23187, however, influx of Ca2+ occurred immediately following activation of the cells. There were no detectable alterations in cytosolic Ca2+ or measurable net efflux or influx of the cation above control levels in PMA-activated neutrophils. These data demonstrate that FMLP, OZ- and A23187-mediated alterations in neutrophil cytosolic Ca2+ are due to mobilization of both intracellular and extracellular cation, while activation of neutrophils by PMA is independent of alterations in cytosolic Ca2+.
Mahomed
A G
AG
Department of Immunology, Institute for Pathology, University of Pretoria, South Africa.
Anderson
R
R
D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007476:Ionophores / Q000494:pharmacology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015054:Zymosan / Q000494:pharmacology
D005456:Fluorescent Dyes; D007476:Ionophores; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015054:Zymosan; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D016257:Fura-2