Mitochondrial Calcium in Heart Cells: Beat-to-Beat Oscillations or Slow Integration of Cytosolic Transients?

Mitochondria have been implicated in intracellular Ca²⁺ signaling in many cell types. Theinner mitochondrial membrane contains Ca²⁺-transporting proteins, which catalyze Ca²⁺ uptakeand extrusion. Intramitochondrial (matrix) Ca²⁺, in turn, regulates the activity of Krebs cycledehydrogenases and, ultimately, the rate of ATP synthesis. In the myocardium, controversyremains whether the fast cytosolic Ca²⁺ transients underlying excitation-contraction couplingin beating cells are rapidly transmitted into the matrix compartment or slowly integratedby the mitochondrial Ca²⁺ transporters. This mini-review critically summarizes the recentexperimental work in this field.