FIGURE 6.

Histamine-induced Ca²⁺ entry on EA.hy926 cells grown on glass. Cytosolic Ca²⁺ concentration was assessed on EA.hy926 cells loaded with 2 μm Fura-2 and stimulated with 1 μm histamine in 2 mm Ca²⁺-containing medium. A, EA.hy926 cells were transiently transfected with control siRNA (scramble, siControl), or siRNA against STIM1 or Orai1. Each trace is the mean of a representative coverslip. B, quantification of the effects of siSTIM1 and siOrai1 on the difference between the ratio at 10 min and the basal ratio (n ranges from 81 to 201 cells). C, representative traces of 1 μm histamine stimulation of cells transiently transfected with siControl or siTRPC3. Each trace represents the mean of a representative coverslip. D, quantification of the effects of siTRPC3, siTRPC4, and siTRPC5 on the difference between the ratio after 10 min of stimulation and the basal ratio (n ranges from 67 to 85 cells). E, EA.hy926 cells were transiently transfected with the ER-targeted cameleon probe D1_ER. Representative recording of a cell stimulated sequentially with 1 μm histamine in Ca²⁺-containing medium and in Ca²⁺-free medium is shown. F, quantification of ER Ca²⁺ release in EA.hy926 cells stimulated by 1 μm histamine in Ca²⁺-containing medium (CA), Ca²⁺-free medium (CF), and by 1 μm thapsigargin (Tg) (in CA). Error bars, S.E. ***, p < 0.001.