Potassium Transference in NiteUa

I N T R O D U C T I O N This study is concerned with the relationship of K + fluxes to the electrically measured membrane conductance and the level o f the resting potential of giant internodal cells of Nitella. In such studies it has been customary to assume that electrogenic ion p u m p i n g is present and that a relatively large passive re turn cur rent serves to electrically balance it. The acceptability o f this idea was greatly influenced by Kitasato's (1968) repor t suggesting the distinct possibility o f H + as the major ion both in active extrusion and in the passive re turn cur ren t (cf. Anderson , 1973). Before this an unresolved problem existed in that the typical measured electrical conductance o f Characean cells was more than 10 times greater than that predicted f rom the resting fluxes o f K +, Na +, and CI(Williams et al., 1964), as calculated by the Goldman (1943) flux equation. This problem was apparent ly solved by attr ibuting the unexplained conductance to H + (Kitasato, 1968). It is to be noted that membrane conductance is computed f rom the displacement o f the resting potential when an applied cur ren t o f known magni tude is J. GEN. PHYSIOL. 9 The Rockefeller University Press 9 0022-1295/78/0801-020351.00 203 on Jne 0, 2017 D ow nladed fom Published August 1, 1978