SLC8A1

In cardiac myocytes, Ca²⁺ concentrations alternate between high levels during contraction and low levels during relaxation. The increase in Ca²⁺ concentration during contraction is primarily due to release of Ca²⁺ from intracellular stores. However, some Ca²⁺ also enters the cell through the sarcolemma (plasma membrane). During relaxation, Ca²⁺ is sequestered within the intracellular stores. To prevent overloading of intracellular stores, the Ca²⁺ that entered across the sarcolemma must be extruded from the cell. The Na⁺-Ca²⁺ exchanger is the primary mechanism by which the Ca²⁺ is extruded from the cell during relaxation. In the heart, the exchanger may play a key role in digitalis action. The exchanger is the dominant mechanism in returning the cardiac myocyte to its resting state following excitation.[supplied by OMIM, Apr 2004]