Neutrophil secretion induced by an intracellular Ca2+ rise and followed by whole-cell patch-clamp recordings occurs without any selective mobilization of different granule populations

Abstract

We have investigated calcium-induced secretion in human neutrophils, using a whole-cell patch-clamp technique. Mobilization of subcellular granules to the cell membrane was followed as the change in membrane capacitance (ΔC m). Both the magnitude and the kinetics of the response differed between low and high concentrations of Ca2+. A sustained secretion following a short lag phase was induced by high concentrations of Ca 2+ (100μM and higher). A stable plateau was reached after 5-7 minutes at ΔCm values corresponding to values expected after all specific as well as azurophil granules have been mobilized. Capacitance values of the same magnitude could be obtained also at lower Ca2+ concentrations, but typically no stable plateau was reached within the measuring time. In contrast to previous studies, we were unable to detect any pattern of secretion corresponding to a distinct submaximal response or selective mobilization of granule subsets specified by their Ca2+ -sensitivity. Copyright © 2006 Daniel Granfeldt et al.