Figure 6.

The fMLF and WKYMVM peptides induce a rise in intracellular calcium, even when extracellular calcium is depleted. Neutrophils loaded with Fura-2 were incubated at 37°C for 5 minutes. Depletion of extracellular calcium was achieved by the addition of EGTA (5 mM; broken lines) 20 seconds before addition of the agonist (time 0). The cells were then stimulated with decreasing concentrations of WKYMVM (lower part of the figure) or fMLF (upper part of the figure). The responses of the control cells (incubated in the absence of EGTA and in the presence of 1 mM calcium) are shown as solid lines. The changes in cytosolic Ca²⁺ levels were determined by measuring the fluorescence emitted at 509 nm following excitation at 340 nm and 380 nm. The traces shown are from a representative experiment of at least five repetitions that gave similar results.