Thus, the exchanger also likely plays an important role in regaining the cell's normal calcium concentrations after an excitotoxic insult.
Another, more ubiquitous transmembrane pump that exports calcium from the cell is the plasma membrane Ca2+ ATPase (PMCA), which has a much higher affinity but a much lower capacity.
[1][8][9] The NCX may operate in both forward and reverse directions simultaneously in different areas of the cell, depending on the combined effects of Na+ and Ca2+ gradients.
Due to the delicate role that Ca2+ plays in the contraction of heart muscles, the cellular concentration of Ca2+ is carefully controlled.
During the resting potential, the Na+/Ca2+ exchanger takes advantage of the large extracellular Na+ concentration gradient to help pump Ca2+ out of the cell.
[13] The family is believed to have arisen from a gene duplication event, due to apparent pseudo-symmetry within the primary sequence of the transmembrane domain.
[18] This clearly illustrates a dimeric transporter of 10 transmembrane helices, with a diamond shaped site for substrate binding.
[19][20][21] In 1968, H Reuter and N Seitz published findings that, when Na+ is removed from the medium surrounding a cell, the efflux of Ca2+ is inhibited, and they proposed that there might be a mechanism for exchanging the two ions.
[2][22] In 1969, a group led by PF Baker that was experimenting using squid axons published a finding that proposed that there exists a means of Na+ exit from cells other than the sodium-potassium pump.
[2][23] Digitalis, more commonly known as foxglove, is known to have a large effect on the Na/K ATPase, ultimately causing a more forceful contraction of the heart.