Ionic changes accompanying astrocytic intercellular calcium waves triggered by mechanical cell damaging stimulation.
Mechanically poking or damaging a single cell within a confluent astrocyte culture produces the so-called intercellular calcium (Ca(2+)) waves, that is, cell-to-cell propagating changes of intracellular free Ca(2+). We were interested whether intercellular Ca(2+) waves are also associated with changes in other intra- or extracellular ions. To that purpose, we investigated spatiotemporal changes of intracellular Ca(2+) (Ca(i)2+), sodium (Na(i)+) and protons (H(i)+) in primary cultures of rat cortical astrocytes using microfluorescence imaging with fura-2, SBFI and BCECF, respectively; changes of extracellular potassium (K(e)+) were monitored with K(+)-sensitive microelectrodes. Mechanical damage to a single cell by stimulation with a piezo-electrically driven micropipette initiated intercellular Ca(2+) waves that propagated to about 160 microm away from the stimulation point. Na(i)(+) increases could be detected in cells located 2-3 cell diameters from the stimulated cell, acidification was observed 1-2 cell diameters away and Ke(+) increases were measured up to 75 microm away. Kinetic analysis suggests that the Na(i)(+) and H(i)(+) changes occur after, and thus secondary to the Ca(i)(2+) changes. In contrast, K(e)(+) changes occurred very fast, even before the Ca(i)(2+) changes, but their propagation speed was too fast to implicate them as a trigger of Ca(i)(2+) changes. As Na(i)(+) is an important regulator of glycolysis in astrocytes, we hypothesize that astrocytic Na(i)(+) changes in cells located remotely from a damaged cell might be a signal that activates glycolysis thereby producing more lactate that is transferred to the neurons and increases their energy potential to survive the inflicted damage.
Paemeleire
K
K
Department of Physiology and Pathophysiology, University of Ghent, De Pintelaan 185 (Blok B), B-9000, Ghent, Belgium.
Leybaert
L
L
D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D018929:Cell Culture Techniques; D006859:Hydrogen / Q000378:metabolism; D007477:Ions; D010812:Physical Stimulation; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism
D007477:Ions; D006859:Hydrogen; D012964:Sodium; D011188:Potassium; D002118:Calcium