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Steady‐state contribution of the sodium pump to the resting potential of a molluscan neurone
Author(s) -
Gorman A. L. F.,
Marmor M. F.
Publication year - 1974
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1974.sp010692
Subject(s) - membrane potential , sodium pump , steady state (chemistry) , ouabain , resting potential , biophysics , sodium , chemistry , membrane , conductance , ion pump , diaphragm pump , ion , biochemistry , biology , materials science , nanotechnology , physics , organic chemistry , micropump , condensed matter physics
1. The electrogenic contribution of the Na + ‐K + exchange pump to the membrane potential of the Anisodoris giant neurone (G cell) was examined under steady‐state and Na + loaded conditions. 2. The membrane potential was variable for the first 1‐4 hr after impalement, but, in the absence of experimental manipulation, remained constant thereafter. The average membrane potential for ten cells maintained at 11–13 °C and measured 5‐36 hr after impalement was 55·8 ± 1·0 mV ( S.E. of mean). 3. Low concentrations of external ACh caused a reversible increase in membrane Na + conductance. Brief exposure to ACh proved a fast and reversible technique to load the cell with Na + ions, and transiently stimulate the electrogenic Na + pump. 4. In ten cells maintained from 5 to 36 hr at 11–13° C the reduction in membrane potential produced by inhibition of the Na + pump with ouabain was remarkably constant between cells and averaged + 9·7 mV. 5. Cells maintained under steady‐state conditions (at 11–13° C) for extended periods of time were shown to be relatively insensitive to changes in temperature and to small changes in external K + . 6. It is estimated that the Na + ‐K + exchange pump contributes approximately ‐ 10 mV to the steady‐state resting potential of the G cell, and that two Na + ions are extruded for every K + ion transported into the cell per pump cycle.