Figure 3. MCa increases ECRE frequency in fibres treated with saponin.

An adult skeletal muscle fibre was loaded with Fluo-4 and treated with saponin as described in Methods. Representative line-scan images were recorded under control conditions (Aa and Ba) or in the presence of 50 nm MCa (Ab and Bb). The internal solution contained either sulphate (A) or glutamate (B) as the major anion. C, representative image from a saponin-treated fibre in the presence of 500 nm [Ala²⁴]MCa analogue in sulphate-based internal solution. D, MCa concentration dependency of event frequency. Filled symbols indicate glutamate while open symbols indicate sulphate as the major anion. Circles, MCa; triangles, [Ala²⁴]MCa.