Pharmacology of Capacitative Calcium Entry

Figure 1.

Capacitative calcium entry can be inhibited by gadolinium ions (Gd³⁺) and activated by thapsigargin.^a

A. Cells (in Ca²⁺-free medium) actively respond to the cholinergic agonist carbachol (100 μM) by releasing internal stores of Ca²⁺ into the cytosol (Peak I). Subsequently supplied external Ca²⁺ is taken up by the cells in the absence (black trace; Peak II) but not in the presence (red trace) of Gd³⁺ (1 μM). Gd³⁺ is thus an inhibitor of capacitative calcium entry.

B. Thapsigargin (1 μM) causes cells (in Ca²⁺-free medium) to leak their internal stores of Ca²⁺ into the cytosol (Peak I). Capacitative calcium entry ensues (black trace; Peak II), which is again inhibited by Gd³⁺ (red trace).

^aData have been simplified from (24).

^bF₃₄₀/F₃₈₀ is the fluorescence shift of the Ca²⁺ indicator Fura-2.