Figure 3. Sequential CPA application reveals an inverse relationship between global [Ca2+]i and store refilling.

Time courses of [Ca2+]i changes recorded from two individual cells in a typical experiment. Extracellular Ca2+ was omitted as indicated and then CPA (30 μM) was applied in Ca2+-free extracellular solution from 10 min. Following the first CPA application, a modified Tyrode solution containing 2 mM Ca2+ was re-applied a second time. Bracekts indicate areas under which [Ca2+]i were integrated to estimate store content during sequential CPA application (CPA1 and CPA2) and global [Ca2+]i elevation during Ca2+ readdition ([Ca2+]SOCE). Values of [Ca2+]i prior to the CPA or extracellular Ca2+ readdition were subtracted before integration. Note that application of ionomycin (Iono, 1 μM) following the second CPA application in both cells generates only a small elevation in [Ca2+]i.