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 (△Cm). 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 Ca2+(100μM and higher). A stable plateau was reached after 5–7 minutes at△Cmvalues 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.