DOES ACTIN POLYMERIZATION STATUS MODULATE CA2- RELEASE AND COALESCENCE CA2+ STORES BY CYTOCHALASINS( STORAGE IN HUMAN NEUTROPHILS )

The aim of this paper was to establish whether actin polymerization mo dulated cytosolic Ca2+ storage in human neutrophils. Over the concentr ation ranges which inhibit actin polymerization, cytochalasins A, B, a nd D liberated Ca2+ from membrane-bound stores within neutrophils. Two Ca2+ storage sites were identified in neutrophils by the accumulation of the Ca2+ binding probe, chlortetracycline: one at the center of th e cell and the other at the cell periphery. Confocal imaging demonstra ted that cytochalasins released Ca2+ from the neutrophil periphery, bu t not from the central Ca2+ store, Ca2+ store release was coupled to C a2+ influx, suggesting that the peripheral site may be a physiological store containing a Ca2+ influx factor, 3,3'-Dihexyloxacarbocyanine io dide staining organelles, which correlate with Ca2+ release sites, coa lesced in neutrophils after treatment with cytochalasins. We propose t hat peripheral Ca2+ storage sites are restricted from coalescence by c ortical polymerized actin and that Ca2+ store coalescence and Ca2+ rel ease are coupled events. (C) 1997 Academic Press.