Discrimination between receptor- and store-operated Ca2+ influx in human neutrophils

Ca2+ and Sr2+ entry pathways activated by pro-inflammatory agonists FMLP, LTB4 and PAF have been compared to thapsigargin in human neutrophils. 2-APB (10 μM) increased Ca2+ influx and to a greater extent in agonist than in thapsigargin stimulated neutrophils. This action of 2-APB was specific to Ca2+ because 2-APB did not augment Sr2+ entry in agonist and thapsigargin stimulated neutrophils. This suggests that Ca2+ and Sr2+ entry can be used to discriminate between receptor and non-receptor (store)-operated Ca2+ influx. Our data show for the first time that Pyr3 whilst partially inhibiting agonist induced Ca2+ influx almost completely abolished Ca2+ influx after thapsigargin stimulation.