Figure 5. Effects of Ba²⁺ and Sr²⁺ on the Orai1/STIM1 currents obtained under different transfection conditions.

A, dependence of the amplitude of the Orai1/STIM1-mediated current at −118 mV on Ba²⁺ and Sr²⁺. Data were obtained in cells transfected with Orai1 and STIM1 plasmids at a molar ratio of either 4 : 1 (trace 1) or 1 : 4 (trace 2). Each point represents the amplitude of the current at −118 mV measured from the responses to voltage ramps ranging from −138 mV to 102 mV and applied every 2 s. Zero-time point corresponds to 60 s after achieving whole cell. B, representative I–V plots of the data shown on panel A. a corresponds to trace 1, and b corresponds to trace 2 on panel A. C, representative current traces in response to steps to −118 mV of the data shown on panel A. a corresponds to trace 1, and b corresponds to trace 2 on panel A. c, the same Ba²⁺ traces as shown on panels a and b but on a shorter time scale. Traces shown on panels B and C were taken 40–60 s after applying Ba²⁺ or Sr²⁺ in the bath.