Osmotically induced cytosolic free Ca(2+) changes in human neutrophils.
Cytosolic free Ca(2+) concentration in neutrophils was measured by ratiometric fluorometry of intracellular fura2. Increasing the extracellular osmolarity, by either NaCl (300-600 mM) or sucrose (600-1200 mM), caused a rise in cytosolic free Ca(2+) (Delta(max) approximately equal to 600 nM). This was not due to cell lysis as the cytosolic free Ca(2+) concentration was reversed by restoration of isotonicity and a second rise in cytosolic free Ca(2+) could be provoked by repeating the change in extracellular osmolarity. Furthermore, the rise in cytosolic free Ca(2+) concentration occurred in the absence of extracellular Ca(2+), demonstrating that release of intracellular fura2 into the external medium did not occur. The osmotically-induced rise in cytosolic free Ca(2+) was not inhibited by either the phospholipase C-inhibitor U73122, or the microfilament inhibitor cytochalasin B, suggesting that neither signalling via inositol tris-phosphate or the cytoskeletal system were involved. However, the rise in cytosolic free Ca(2+) may have resulted from a reduction in neutrophil water volume in hyperosmotic conditions. As these rises in cytosolic Ca(2+) (Delta(max) approximately equal to 600 nM) were large enough to provoke changes in neutrophil activity, we propose that conditions which removes cell water may similarly elevate cytosolic free Ca(2+) to physiologically important levels.
Morris
M R
MR
Molecular Signalling Group, Department of Surgery, University of Wales College of Medicine, Cardiff, UK.
Doull
I J
IJ
Hallett
M B
MB
D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D048429:Cell Size; D003600:Cytosol / Q000378:metabolism*; D016257:Fura-2; D006801:Humans; D007552:Isotonic Solutions; D018375:Neutrophil Activation; D009504:Neutrophils / Q000378:metabolism*; D009994:Osmolar Concentration; D012965:Sodium Chloride
D007552:Isotonic Solutions; D012965:Sodium Chloride; D002118:Calcium; D016257:Fura-2