Sodium-calcium exchange in heart: membrane currents and changes in [Ca2+]i.
Recordings have been made of changes in intracellular calcium ion concentration ([Ca2+]i) that can be attributed to the operation of an electrogenic, voltage-dependent sodium-calcium (Na-Ca) exchanger in mammalian heart cells. Guinea pig ventricular myocytes under voltage clamp were perfused internally with fura-2, a fluorescent Ca2+-indicator, and changes in [Ca2+]i and membrane current that resulted from Na-Ca exchange were identified through the use of various organic channel blockers and impermeant ions. Depolarization of cells elicited slow increases in [Ca2+]i, with the maximum increase depending on internal [Na+], external [Ca2+], and membrane voltage. Repolarization was associated with net Ca2+ efflux and a decline in the inward current that developed instantaneously upon repolarization. The relation between [Ca2+]i and current was linear, and the slope was made steeper by hyperpolarization.
Department of Physiology, University of Maryland School of Medicine, Baltimore.
L
L
Barcenas-Ruiz
D J
DJ
Beuckelmann
W G
WG
Wier
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D019831:Sodium-Calcium Exchanger; D016276:Ventricular Function
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D002118:Calcium