Fig. 1.

Patterns of intracellular of Ca²⁺ signaling in Ca²⁺-sensing receptor (CaR)HEK-293 cells. Starting from a resting concentration of 1.5 mM CaCl₂, CaRHEK-293 cells were perfused with a solution containing 3 mM CaCl₂ (upward arrow) for 200–300 s as indicated before return to perfusion containing 1.5 mM CaCl₂ (downward arrow). A: typical tracing of an oscillatory response induced by increasing extracellular Ca²⁺ concentration ([Ca²⁺]_e). B: peak and plateau response without intracellular Ca²⁺ concentration ([Ca²⁺]_i) oscillations. Bottom trace: perfusion with 2.25 mM CaCl₂. C: in some cases the pattern shown in B was preceded by [Ca²⁺]_i spikes of diminishing amplitude. D: percentage of cells with each type of response (756 cells; n.r., not responding). In subsequent figures, the results are presented as the percentage of oscillating and nonoscillating cells in the population.