Figure 2.

OR51E2-agonist induces Ca²⁺ signals in human RPE cells. (A) Representative Ca²⁺ imaging trace of a primary RPE cell. Horizontal bars indicate time and duration of stimulus application. β-ionone (100 μM) application induces a transient rise in intracellular Ca²⁺ in the individual cells. ATP (100 μM) served as the positive stimulus to control cell viability. Cytosolic Ca²⁺ levels were monitored as an integrated f₃₄₀/f₃₈₀ fluorescence ratio, which is expressed as a function of time. In prolonged stimulation, the maximal signal amplitude was reached after a 3 min application of β-ionone. β-ionone induced transient Ca²⁺ signals in primary RPE cells upon repetitive stimulation. (B) The β-ionone-induced Ca²⁺ increase is dose-dependent. β-ionone was applied at different concentrations to ensure the maximal number of responsive cells. The number of responsive cells was normalized to the number of ATP-responsive cells [positive control (n = 5–7)]. (C) Representative Ca²⁺ imaging trace of a Fura-2-loaded human RPE cells. Application of β-ionone induces intracellular Ca²⁺ increase in a dose-dependent manner (upper panel). Application of the solvent (0.1% DMSO) did not result in any changes in cytosolic Ca²⁺ level (lower panel). (D) Dose-response curve of the β-ionone-induced Ca²⁺ signals. The signal amplitude, at the first application, was normalized to the amplitude evoked by ATP and is displayed as a function of the applied β-ionone concentration. The EC₅₀ value was 91 μM. (n = 5–7).