Abstract |
During early myocardial ischemia, the myocytes are loaded with Na(+), which in turn leads to Ca(2+) overload and cell death. The pathway of the Na(+) influx has not been fully elucidated. The aim of the study was to quantify the Na(+) inward current through sarcolemmal KATP channels (IKATP,Na) in anoxic isolated cardiomyocytes at the actual reversal potential (Vrev) and to estimate the contribution of this current to the Na(+) influx in the ischemic myocardium. IKATP,Na was determined in excised single channel patches of mouse ventricular myocytes and macropatches of Xenopus laevis oocytes expressing SUR2A/Kir6.2 channels. In the presence of K+ ions, the respective permeability ratios for Na(+) to K(+) ions, PNa/PK, were close to 0.01. Only in the presence of Na(+) ions on both sides of the membrane was IKATP,Na similarly large to that calculated from the permeability ratio PNa/PK, indicative of a Na(+) influx that is largely independent of the K+ efflux at Vrev. With the use of a peak KATP channel conductance in anoxic cardiomyocytes of 410 nS, model simulations for a myocyte within the ischemic myocardium showed that the amplitude of the Na(+) influx and K(+) efflux is even larger than the respective fluxes by the Na(+) - K(+) pump and all other background fluxes. These results suggest that during early ischemia the Na(+) influx through KATP channels essentially contributes to the total Na+ influx and that it also balances the K(+) efflux through KATP channels.
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Authors | Christian Bollensdorff, Andreas Knopp, Christoph Biskup, Thomas Zimmer, Klaus Benndorf |
Journal | American journal of physiology. Heart and circulatory physiology
(Am J Physiol Heart Circ Physiol)
Vol. 286
Issue 1
Pg. H283-95
(Jan 2004)
ISSN: 0363-6135 [Print] United States |
PMID | 12919930
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Potassium Channels
- Adenosine Triphosphate
- Sodium
- Potassium
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Topics |
- Adenosine Triphosphate
(physiology)
- Animals
- Cell Hypoxia
- Electric Conductivity
- Electrophysiology
- Mice
- Models, Biological
- Myocardial Ischemia
(metabolism)
- Myocardium
(metabolism)
- Myocytes, Cardiac
(metabolism)
- Oocytes
- Permeability
- Potassium
(metabolism)
- Potassium Channels
(physiology)
- Sarcolemma
(metabolism)
- Sodium
(metabolism, physiology)
- Xenopus laevis
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