Ca2+ signalling in rat chromaffin cells: interplay between Ca2+ release from intracellular stores and membrane potential
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Dissection of Local Ca2+ Signals in Cultured Cells by Membrane-targeted Ca2+ Indicators
Published on: March 22, 2019
1Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Trieste, Italy.
Abstract:
Cytosolic Ca2+ oscillations are physiologically important in a range of excitable and non-excitable cells. The combined techniques of whole-cell patch clamp and photometric measurement of cytosolic Ca2+ has enabled us to identify the components of Ca2+ spiking in rat chromaffin cells. We show that Ca2+ oscillations continue at a fixed membrane potential and that infusion of the InsP3 receptor antagonist, heparin, substantially blocked the cytosolic Ca2+ spikes. However, even in the presence of heparin we observed spikes of membrane potential depolarization due to the repetitive activation of a transient inward cation current. We conclude that Ca2+ oscillations are dependent on Ca2+ release from heparin sensitive Ca2+ stores and possibly on Ca2+ entry associated with the repetitive activation of a transient cation current. The depolarizing action of the cation current would, in turn, recruit voltage-sensitive Ca2+ channels and further Ca2+ entry would augment the cytosolic Ca2+ spikes. Our results demonstrate that Ca2+ oscillations in rat chromaffin cells are due to a complex interplay of Ca2+ entry and Ca2+ release.
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