FIG. 4.

Hp(2-20)-induced calcium mobilization in transfected HL-60 cells. Changes in cytosolic calcium in undifferentiated HL-60 cells stably transfected with either FPR or LXA₄R/FPRL1 were measured by Fura-2 fluorescence. HL-60 cells transfected with LXA₄R/FPRL1 (A) and stimulated with Hp(2-20) (1 μM) or WKYMVm (10 nM; inset) responded with a rise in the intracellular calcium concentration. Cells transfected with FPR (B) showed an increase in intracellular calcium concentration when they were stimulated with a formylated peptide (fMLFK, 10 nM; inset) but not when they were stimulated with Hp(2-20) (10 μM). The arrows indicate the addition of agonists. (C) Relative increase in the cytosolic calcium concentration induced by different concentrations of Hp(2-20) in LXA₄R/FPRL1-expressing cells. Peak values for the different Hp(2-20) concentrations are given as a percentage of the maximal peak value (obtained at 10 μM).