Figure 1. Endothelin-1 (ET-1)-induced InsP₃R Ca²⁺ release in atrial myocytes.

Time series of InsP₃-induced Ca²⁺ release events expressed as F/F₀ of fluo-3 fluorescence obtained in atrial myocytes. Cells were loaded with 5 μm fluo-3 AM (Biotium) for 20 min and left for de-esterification for 15 min before time series were collected in resting cells. A, the InsP₃ pathway was stimulated with 100 nm ET-1 causing a substantial increase in SR-Ca²⁺ release event activity. B, inhibition of ET-1-triggered Ca²⁺ events with 5 μm 2-aminoethoxydiphenyl borate (2APB). C, spontaneous Ca²⁺ event activity under control conditions. SR-Ca²⁺ load was measured at the end of each experiment and found to be not significantly different in the various conditions (Ctrl: 3.45 ± 0.28 F/F₀; ET-1: 3.89 ± 0.48 F/F₀; 2APB + ET-1: 3.84 ± 0.53 F/F₀). Bar graphs represent averaged F/F₀ of the first 20 s (Ctrl) and 160–200 s; scale bars represent 10 μm, N= 3, n= 4–9.