Na-Ca Exchange in Cardiac Sarcolemmal Vesicles
Every second of a heart cell’s existence is characterized by large fluctuations in the cytoplasmic concentration of calcium ions. Accordingly, heart cells exhibit a very sophisticated mechanism for the regulation of their cytoplasmic calcium concentration ([Ca2+]j), a system which involves the coordinated interaction of Ca2+ channels and pumps in the plasma membrane and intracellular organelles as well as Ca-binding proteins in both the cytoplasm and, of course, the myofibrillar apparatus itself. One element of this complex mechanism for regulating [Ca]j is the Na-Ca exchange system, a carrier-mediated transport process in which the movement of Ca2+ in one direction across the membrane is directly coupled to the movement of Na+ in the opposite direction. It is a component of the cardiac plasma membrane (sarcolemma) and mediates Ca2+ movements in either direction between the cell cytoplasm and the extracellular fluid. As discussed in detail elsewhere (1,2), its primary physiological role is probably to serve as a Ca2+ pump, i.e. to effect the net efflux of Ca2+ from the myocardial cell, although it seems likely that under some circumstances it can bring about the net entry of Ca2+ as well.
KeywordsVesicle Preparation Squid Axon Exchange Carrier Native Vesicle Redox Reagent
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- 4.Baker, P.F., Blaustein, M.P., Hodgkin, A.L. and Steinhardt, R.A. J. Phsiol. (London) 200:431–458 (1969).Google Scholar
- 6.Baker, P.F. and Allen, T.J.A., in Bronner, F. and Peterlik, M. (eds) “Calcium and Phosphate Transport Across Biomembranes, Proceedings 2nd International Workshop”. (Liss, New York) pp. 89–94 (1984).Google Scholar
- 19.Reeves, J.P. and Poronnik, P., Am. J. Physiol. (in press) (1987).Google Scholar
- 20.de la Pena, P. and Reeves, J.P., Am. J. Physiol. (in press) (1987).Google Scholar
- 22.Bailey, CA. and Reeves, J.P., Fed. Proc. (in press) (1987).Google Scholar
- 23.Slaughter, R., Welton, A. and Morgan, D., Biophys. J. 49:546a (1986).Google Scholar
- 25.Bailey, CA. and Reeves, J.P., Biophys. J. 49:345a (1986)Google Scholar
- 27.Carafoli, E., (personal communication).Google Scholar
- 28.Reeves, J.P., (unpublished observations).Google Scholar
- 34.Philipson, K.D. and Nishimoto, A.Y., J. Biol. Chem. 257:5111–5117 (1983).Google Scholar