A confocal laser scanning technique was used to provide optical sections in the vertical plane through living neutrophils during engagement of integrin and shape change. This has permitted the visualisation of cytosolic free Ca2+ rises localised to the sites of integrin immobilisation. These localised Ca2+ changes resulted from the release of Ca2+ from intracellular stores, and were not inhibited by removal of extracellular Ca2+ or by the Ca2+ channel blocking nickel ions. After integrin engagement and initial cell shape changes, a second rapid phase of cell spreading occurred, which was accompanied by global Ca2+ signalling bursts that continued sporadically after maximum spreading. This global signalling was driven mainly by Ca2+ influx from the extracellular medium. We propose that the localised and global Ca2+ signalling triggered by integrin engagement results from a common underlying mechanism and these signals are important for neutrophil shape change and extravasation.

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