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. 2010 Aug;10(4):209–218. doi: 10.1124/mi.10.4.4

Figure 1.

Figure 1

Measuring store-operated calcium entry and Icrac. A) Receptor agonists and Ca2+-depleting agents (e.g., thapsigargin) induce a biphasic increase in cytoplasmic Ca2+, most clearly revealed by protocols involving discharge of Ca2+ stores in the absence of extracellular Ca2+ (dotted line) followed by restoration of extracellular Ca2+. B) The current underlying store-operated Ca2+ entry, Icrac, is generally measured by means of the whole-cell patch-clamp technique, utilizing IP3 and a calcium chelator in the patch pipet solution to deplete Ca2+ stores. C) Depletion of Ca2+ stores while measuring whole-cell currents reveals a relatively slowly developing inward current, Icrac. Depending on the recording configuration and cell types, these currents are typically small, in the range of 0.5 – 3.0 pA/pF. D) Icrac shows strong inward rectification in the current–voltage relationship, as is expected for a Ca2+-selective channel as intracellular Ca2+ concentrations are extremely low.