Figure 6. Calcium increase induced by α-ionone, β-ionone or mixtures of α-ionone and β-ionone on HEK293 cells transiently transfected with OR51E2.
HEK 293 cells were transiently transfected to express OR51E2 or mock-transfected (control). 72 h later, cells were loaded with the calcium sensitive dye Fluo-4 and stimulated with (A) α-ionone (10−8 to 10−4 M), mixed or not with 1 μM β-ionone or (B) β-ionone (10−8 to 10−5 M). β-ionone was also applied at 10−4 M, but the response of control cells was near the response of OR51E2 expressing cells (control cells: ΔF/F = 13.77 ± 5.5 %; OR51E2 expressing cells: ΔF/F = 16.84 ± 3 %), so this point is not shown due to lack of specificity. Yet, the response induced by 10−4 M β-ionone on OR51E2 expressing cells is not higher than the one induced by 10−6 M β-ionone. Calcium responses due to the interaction between the OR and odorant molecules are expressed as the mean fluorescence variation ΔF/F (%). (filled symbols) OR51E2 cells; (open symbols) control cells; bars indicate standard deviation (n ≥ 3).