Actions of calcium influx blockers in human neutrophils support a role for receptor-operated calcium entry

The action of two potent store operated Ca2+ entry (SOCE) inhibitors, ML-9 and GdCl3 on Ca2+ fluxes induced by the pro-inflammatory agonists FMLP, PAF, LTB4 as well as the receptor-independent stimulus thapsigargin has not been documented in human neutrophils. In this study, ML-9 enhanced both release and subsequent Ca2+ influx in response to agonists whereas it enhanced Ca2+ release by thapsigargin, but inhibited Ca2+ influx. In contrast, 1 μM GdCl3 completely inhibited Ca2+ influx in response to thapsigargin, but only partially blocked Ca2+ influx after agonist stimulation. These results strongly suggest a major role for receptor-operated Ca2+ influx in human neutrophils.