Role of Ca2+ and Mg2+ in some human neutrophil functions as indicated by ionophore A23187

Studies with the divalent cation ionophore A23187 suggest that both Ca2+ and Mg2+ ion influx play a role in human peripheral blood neutrophil function. Degranulation of neutrophils occurred at ionophore concentrations of 10(-5) M and was Ca2+ but not Mg2+ dependent. Modulation of neutrophil chemotaxis was enhanced optimally by 10(-7) M ionophore and was both Ca2+ and Mg2+ dependent. Concentrations of ionophore as low as 10(-12) M seemed to sensitize the cells to a concentration of phorbol myristate acetate which by itself was not chemotactic. These findings also indicate that factors other than Ca2+ or increases in cyclic nucleotides are important to initiation and modulation of neutrophil function.