Na-Ca exchange: stoichiometry and electrogenicity.

摘要: This review discusses the evidence concerning stoichiometry of Na-Ca exchange. In particular we consider whether exchange has been shown to transport more than two Na+ ions per Ca2+ ion and therefore it generates an electric current. The first part this both direct indirect its possible voltage dependence. We find that, although there is some suggesting that may for each ion, most available equivocal cannot fix precisely. Furthermore, using a simple explicit circulating carrier model exchange, show effect membrane potential on be considerably complicated generally believed. electrogenic electroneutral exchanges will affected by potential. conclude demonstration dependence does not necessarily imply electrogenic. Additionally, analysis shows apart from restricted range near thermodynamic equilibrium, impossible predict either magnitude or direction effects second any known currents attributed show, in contrast previous suggestions, can theoretically produce current appears activated intracellular Ca reversal However, experimental given produced hampered existence other Ca- Na-dependent currents. conclusion, feel no allows unambiguously identified with