Studying mitochondrial Ca2+ uptake - A revisit

► Mitochondrial Ca2+ sequestration was tested by various techniques. ► Kinetics and Ca2+ sensitivity of mitochondrial Ca2+ uptake depends on the techniques chosen. ► By electrophysiology, 2 and 3 distinct Ca2+ inward currents were measured in HeLa and endothelial cell mitoplasts. ► Mitoplast Ca2+ inward currents differ in frequency of appearance and conductance ranging from 7.6 to 74.3 pS. ► Mitochondrial Ca2+ uptake routes/modes exists and might be cell specific.