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. 1967 Jan;188(2):235–260. doi: 10.1113/jphysiol.1967.sp008136

Intracellular sodium concentration and resting sodium fluxes of the frog heart ventricle

Mary J Keenan, R Niedergerke
PMCID: PMC1396003  PMID: 6030516

Abstract

1. Using 24Na to label the exchangeable sodium in the tissue and either [35S]sulphate or [14C]sucrose to label the extracellular spaces, the intracellular sodium concentration of frog heart ventricles was determined and found to be between about 5 and 10 m-mole/kg cell water.

2. The intracellular potassium concentration, obtained by flame-photometric analysis, was approximately 163 m-mole/kg cell water.

3. Two different methods were employed to study the sodium tracer efflux of resting heart ventricles. One involved a double-tracer technique, using 24Na to indicate the release of the exchangeable tissue sodium, and 35SO4 to indicate, approximately, the release of extra-myocardial sodium. In the other a comparison was made of the sodium release from the tissue when it contained sodium either at the normal concentration or at a concentration enhanced by exchange with intracellular potassium.

4. The magnitude of the sodium efflux from heart fibres as measured by both methods was of the order 50-100 p-mole/cm2 sec. Simultaneously with this cellular efflux a substantial amount of sodium was released from extra-myocardial spaces and tissues.

5. The net efflux of potassium ions from heart cells that occurred when heart ventricles were perfused with potassium-depleted fluids was determined. The results were used to obtain an indirect estimate, of about 2-3 p-mole/cm2 sec, for the resting sodium influx.

6. The significance of these different values of sodium efflux and influx is discussed.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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