Localized superoxide release by neutrophils can be provoked by a cytosolic calcium 'cloud'

Immunology. 1991 Jun;73(2):228-34.


We have used single-cell ratio imaging of Fura-2 loaded neutrophils to visualize release of cytosolic Ca2+ from an intracellular store in order to determine the location of this store and the relationship of release from it to oxidase activation. In the presence of extracellular Ca2+, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) produced an increase in free Ca2+ throughout the cytosol. In its absence, however, stimulation induced in 38% of neutrophils a highly localized increase in cytosolic free Ca2+, located between the nuclear lobes and the plasma membrane, at a region of cytosol which stained positively with 3,3'-dihexyloxacarbocyanine iodide [DiOC6(3)]. Calcium release from the store was transient, without oscillation and occurred after delays of up to 120 seconds. Addition of Ca2+ ionophore also released Ca2+ from this, and other stores, within the cell, up to three foci being detected in some cells. Localized oxidase activation occurred at the plasma membrane when the calcium concentration ([Ca2+]) of the 'cloud' exceeded 250 nM. Surprisingly, localized activation occurred at the plasma membrane at a site separate from but near to a region of high Ca2+. It was concluded that release of Ca2+ from a single receptor-releasable, Ca2+ store in neutrophils was insufficient to trigger oxidase activation throughout the cell, but could provide a localized activation of the oxidase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / blood*
  • Cell Membrane / metabolism
  • Cell Nucleus / metabolism
  • Cells, Cultured
  • Cytosol / metabolism*
  • Fura-2
  • Humans
  • Ionomycin / pharmacology
  • N-Formylmethionine Leucyl-Phenylalanine / pharmacology
  • Neutrophils / drug effects
  • Neutrophils / metabolism*
  • Oxidoreductases / blood
  • Superoxides / blood*


  • Superoxides
  • Ionomycin
  • N-Formylmethionine Leucyl-Phenylalanine
  • Oxidoreductases
  • Calcium
  • Fura-2