Isolation of I_MCU by applying intracellular Ca²⁺ chelators. (A) Currents induced by 20 mM extracellular Ca²⁺ in the presence (red) or absence (black) of 1 µM Ru360. Oocytes were preinjected with 5 nmol EGTA and were constantly exposed to 0.5 mM niflumic acid during recordings. (B) I_MCU, obtained by subtracting Ru360-insentive currents (red in A) from total currents (black in A). (C) Currents in uninjected control. Adding Ru360 (red trace) does not affect currents. All traces were digitally filtered at 100 Hz.