Extracellular calcium sensing by glial cells: low extracellular calcium induces intracellular calcium release and intercellular signaling.
Parole chiave
Astratto
Glial cells in primary mixed cultures or purified astrocyte cultures from mouse cortex respond to reduced extracellular calcium concentration ([Ca2+]e) with increases in intracellular calcium concentration ([Ca2+]i) that include single-cell Ca2+ oscillations and propagated intercellular Ca2+ waves. The rate and pattern of propagation of low [Ca2+]e-induced intercellular Ca2+ waves are altered by rapid perfusion of the extracellular medium, suggesting the involvement of an extracellular messenger in Ca2+ wave propagation. The low [Ca2+]e-induced Ca2+ response is abolished by thapsigargin and by the phospholipase antagonist U73122. The low [Ca2+]e-induced response is also blocked by replacement of extracellular Ca2+ with Ba2+, Zn2+, or Ni2+, and by 100 microM La3+. Glial cells in lowered [Ca2+]e (0.1-0.5 mM) show an increased [Ca2+]i response to bath application of ATP, whereas glial cells in increased [Ca2+]e (10-15 mM) show a decreased [Ca2+]i response to ATP. These results show that glial cells possess a mechanism for coupling between [Ca2+]e and the release of Ca2+ from intracellular stores. This mechanism may be involved in glial responses to the extracellular environment and may be important in pathological conditions associated with low extracellular Ca2+ such as seizures or ischemia.