RECEPTOR-MEDIATED CALCIUM-ENTRY IS REQUIRED FOR MAXIMAL EFFECTS OF PLATELET-ACTIVATING-FACTOR PRIMED RESPONSES IN HUMAN NEUTROPHILS

The effect of receptor mediated calcium entry (RMCE) on platelet activ ating factor (PAF) stimulated human neutrophils (PMNs) was investigate d using SKF 96365, a selective inhibitor of RMCE, Changes in cytosolic calcium concentration were determined by the fluorometric dye indo-1, AM, superoxide generation by cytochrome c reduction, and CD11b surfac e expression by how cytometry, SKF 96365 pre-treatment diminished the cytosolic calcium rise in PAF primed PMNs, SKF 96365 treatment signifi cantly (p<0.05) decreased superoxide generation in PAF primed PMNs, bu t did not affect activation of the PMN oxidase by fMLP or PMA. Chelati on of extracellular calcium by EGTA, intracellular calcium by BAPTA, A M, and RMCE blockade by SKF 96365 all statistically inhibited the PAF induced increase in surface expression of CD11b (p<0.05); moreover, SK F 96365 inhibited to a greater extent than EG;TA or BAPTA, ARI treatme nt, These results suggest that RMCE is required for maximal effects of PAF on PMN function. (C) 1997 Academic Press.