|
|
|
|
|
|
|
||
The Journal of General Physiology, Vol 80, 325-351, Copyright © 1982 by The Rockefeller University Press
ARTICLES |
SS Sheu and HA Fozzard
Na+- and CA2+-sensitive microelectrodes were used to measure intracellular Na+ and Ca2+ activities (alpha iCa) of sheep ventricular muscle and Purkinje strands to study the interrelationship between Na+ and Ca2+ electrochemical gradients (delta muNa and delta muCa) under various conditions. In ventricular muscle, alpha iNa was 6.4 +/- 1.2 mM and alpha iCa was 87 +/- 20 nM ([Ca/+] = 272 nM). A graded decrease of external Na+ activity (alpha oNa) resulted in decrease of alpha iNa, and increase of alpha iCa. There was increase of twitch tension in low- alpha oNa solutions, and occasional increase of resting tension in 40% alpha oNa. Increase of external Ca2+ (alpha oCa) resulted in increase of alpha iCa and decrease of alpha iNa. Decrease of alpha oCa resulted in decrease of alpha iCa and increase of alpha iNa. The apparent resting Na-Ca energy ratio (delta muCa/delta muNa) was between 2.43 and 2.63. When the membrane potential (Vm) was depolarized by 50 mM K+ in ventricular muscle, Vm depolarized by 50 mV, alpha iNa decreased, and alpha iCa increased, with the development of a contracture. The apparent energy coupling ratio did not change with depolarization. 5 x 10(-6) M ouabain induced a large increase in alpha iNa ad alpha iCa, accompanied by an increase in twitch and resting tension. Under the conditions we have studied, delta muNa and delta muCa appeared to be coupled and n was nearly constant at 2.5, as would be expected if the Na-Ca exchange system was able to set the steady level of alpha iCa. Tension threshold was about 230 nM alpha iCa. The magnitude of twitch tension was directly related to alpha iCa.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Cortassa, M. A. Aon, B. O'Rourke, R. Jacques, H.-J. Tseng, E. Marban, and R. L. Winslow A Computational Model Integrating Electrophysiology, Contraction, and Mitochondrial Bioenergetics in the Ventricular Myocyte Biophys. J., August 15, 2006; 91(4): 1564 - 1589. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Tanaka, H. Uchikado, S. Niiyama, K. Uematsu, and H. Higashi Extrusion of Intracellular Calcium Ion After In Vitro Ischemia in the Rat Hippocampal CA1 Region J Neurophysiol, August 1, 2002; 88(2): 879 - 887. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. S. Mihailidou, H. Bundgaard, M. Mardini, P. S. Hansen, K. Kjeldsen, and H. H. Rasmussen Hyperaldosteronemia in Rabbits Inhibits the Cardiac Sarcolemmal Na+-K+ Pump Circ. Res., January 7, 2000; 86(1): 37 - 42. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. F. Stowe, S. Fujita, J. An, R. A. Paulsen, S. G. Varadarajan, and S. C. Smart Modulation of myocardial function and [Ca2+] sensitivity by moderate hypothermia in guinea pig isolated hearts Am J Physiol Heart Circ Physiol, December 1, 1999; 277(6): H2321 - H2332. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. P. Blaustein and W. J. Lederer Sodium/Calcium Exchange: Its Physiological Implications Physiol Rev, July 1, 1999; 79(3): 763 - 854. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L Barcenas-Ruiz, D. Beuckelmann, and W. Wier Sodium-calcium exchange in heart: membrane currents and changes in [Ca2+]i Science, December 18, 1987; 238(4834): 1720 - 1722. [Abstract] [PDF]
|
|
|
|
|
|
L Cleemann, G Pizarro, and M Morad Optical measurements of extracellular calcium depletion during a single heartbeat Science, October 12, 1984; 226(4671): 174 - 177. [Abstract] [PDF]
|
|
|
|
 |
|
 K. Ishihara, D.-H. Yan, S. Yamamoto, and T. Ehara Inward rectifier K+ current under physiological cytoplasmic conditions in guinea-pig cardiac ventricular cells J. Physiol., May 1, 2002; 540(3): 831 - 841. [Abstract] [Full Text] [PDF]
|
|
|
|
