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Na/K Pump Current in Guinea Pig Cardiac Myocytes and the Effect of Na Leak
Author(s) -
DOBRETSOV MAXIM,
STIMERS JOSEPH R.
Publication year - 1997
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.1997.tb00834.x
Subject(s) - ouabain , biophysics , membrane potential , patch clamp , transmembrane protein , leak , guinea pig , membrane , myocyte , sodium , pipette , voltage clamp , chemistry , medicine , biochemistry , electrophysiology , biology , receptor , organic chemistry , environmental engineering , engineering
Na/K Pump Current. Introduction : Steady‐State Na/K pump current (I p ) in adult guinea pig ventricular myocytes was studied to determine the effect on the Na/K pump of transmembrane Na leak, membrane potential, and pipette Na concentration. Methods and Results : Using conventional whole cell, patch clamp techniques, I p was identified as either K 0 ‐sensitive or ouabain‐sensitive current when most other membrane currents were inhibited. Control experiments showed that there were no K 0 ‐sensitive currents other than I p under the conditions of our experiments. I p was found to be similar to that reported by others being voltage dependent between −130 and 0 mV and having a half maximal activation hy Na i of 28 mM. Ouabain sensitivity was also measured, and it was found that there were two binding sites with the high affinity site comprising 5% to 10% of the total and having an apparent affinity 1000‐fold higher than the low affinity site. Apparent affinity of both sites was shifted about 10‐fold (higher affinity) by increasing Na i from 10 to 85 mM. When internally perfused with 0 Na solution, Na leak through the membrane was found to be linearly related to Na/K pump activity. In contrast to prior suggestions, I p was not correlated with series resistance when there was a large transmembrane Na gradient. Conclusion : These data suggest that, under conditions of high transmembrane Na gradient, Na leak through the membrane plays a significant role in determining Na/K pump activity.