Two For-Met–Leu–Phe-OMe analogues trigger selective neutrophil responses: A differential effect on cytosolic free Ca2+

Abstract For-Thp–Leu–Ain-OMe and for-Met–Δ z Leu–Phe-OMe are two conformationally restricted fMLP-OMe analogues able to discriminate between different biological responses of human neutrophils. In this paper, we demonstrate that the former peptide, which evokes only chemotaxis, does not alter human neutrophil Ca 2+ levels. In contrast, for-Met–Δ z Leu–Phe-OMe, which induces superoxide anion release and degranulation but not chemotaxis, significantly increases the cation concentration. The chelation of Ca 2+ in both extracellular and intracellular media abolishes O − 2 production triggered by for-Met–Δ z Leu–Phe-OMe, while the same procedure does not affect neutrophil chemotaxis towards for-Thp–Leu–Ain-OMe. We therefore suggest that chemotaxis, unlike superoxide anion release, is independent of Ca 2+ enhancement in human neutrophils.