Distribution and efflux of sodium from frog heart ventricles perfused with normal and sodium free ringer's solution

Summary

The marked reduction in the rate of²²Na washout in choline Ringer's allowed estimation of resting and beating influx of sodium into the myocardial cell to be made. The influx of sodium into the quiescent myocardium as determined by our technique was 2.0 p mol/cm² sec and the influx per beat amounted to 4.4 p mol/cm² beat. The²²Na that entered the beating ventricle washed out at a much slower rate into choline Ringer than did the²²Na that entered the quiescent ventricle. The sodium that entered while beating mixed with an intracellular sodium pool whose size was estimated at 4 mM Na/kg wet wgt.

The total sodium content of a frog ventricle persufed for 90 min was 50 mM/kg wet wgt which was partitioned in the following manner: Inulin space 28 mM/kg interstitial bound sodium 6 mM/kg; intracellular 16 mM/kg of which 4 mM/kg is in fiber water, the remaining being compartmentalized outside the fiber water volume.

In addition it was found that removal of calcium from choline Ringer increased sodium efflux by 50%.