Ein Vergleich zwischen Fluxmessungen und elektrischen Messungen am Myokard
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1. On the basis of preceeding measurements of the K and Na transmembrane fluxes in resting frog atria and of membrane potential and intracellular K and Na concentrations, the K and Na conductances and permeabilities of resting fibres are calculated. It is assumed that a) the K and Na fluxes are purely passive in the direction of the gradient of the electrochemical potential but composed of an active and a passive part in the opposite direction, and b) there is an independence between passive influx and efflux.
2. The conductances calculated in this manner markedly differ from the conductances determined on the basis of electrophysiological measurements. The K conductance based on tracer experiments is much smaller than the K conductance based on electrical methods; and further, the ratio K: Na conductance calculated from flux measurements is much lower than to be expected from electrical determinations.
3. Possible explanations for this discrepancy are discussed. It is suggested that a correction of the above basic assumptions on the ionic movements could reconcile the results of the flux measurements and the electrical methods: If there is exchange diffusion for Na ions as proposed by Ussing (1949b), and if there is interaction between the passive K influx and efflux hindering each another, the K and Na conductances calculated from the fluxes approach the electrical values.
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