Potassium Exchange in the Dog Heart in Situ

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Abstract
Coronary perfusion with constant flow and constant specific activity permitted an estimate of the transmembrane fluxes of potassium in both directions in the dog heart in situ. The determination of efflux was based on the washout characteristics. Perfusion pressure and coronary flow within the limits studied have little influence on efflux. The estimate of influx involved correction of experimental data using the efflux from the same experiment and is therefore less accurate; it is subject to changes due to alterations in collateral blood supply of the perfusion area. The efflux varies by 50% from heart to heart, averaging 0.68 mEq K + /kg and min at an average heart rate of 130 beats/min. Changes in heart rate reveal that 1.65 µEq K + /kg are exchanged per beat above the resting flux of the nonbeating heart; the latter was estimated by extrapolation to be 0.55 mEq K + /kg and min.