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Effects of anions and cations on the resting membrane potential of internally perfused barnacle muscle fibres
Author(s) -
Lakshminarayanaiah N.,
Rojas E.
Publication year - 1973
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.1973.sp010326
Subject(s) - chemistry , inorganic chemistry , membrane potential , bromide , chloride , tris , oxalate , nuclear chemistry , biochemistry , organic chemistry
1. Single barnacle muscle fibres from Megabalanus psittacus (Darwin) were internally perfused with a number of K salt solutions (200 m M ) which were made isotonic to the barnacle saline with sucrose. 2. 200 m M ‐K acetate solution, in general, was found to be more effective than other solutions of K salts in generating and maintaining stable resting membrane potential of −56·0 ± 0·7 mV (all potentials are referred to the external solutions as ground). The various K salts, on the basis of the magnitude of the resting potential they generated in the muscle fibres, followed the sequence, acetate > isethionate > aspartate > glutamate > fluoride > monohydrogen phosphate > succinate > citrate > sulphate > oxalate > iodobenzoate > ferrocyanide > chlorate > nitrate > chloride > thiocyanate > iodide > bromide > cyanide. 3. The resting potential in muscle fibres perfused with solutions of acetate, aspartate and glutamate increased linearly with the logarithm of the K concentration (slope = 30·4 mV for K acetate and 27·4 for K aspartate and glutamate) when the ionic strength of the solutions was progressively increased from 50 to 650 m M . On the other hand, similar increase of ionic strength beyond 200 m M of solutions of K isethionate, fluoride, monohydrogen phosphate, succinate and citrate depolarized the muscle fibres. 4. Perfusion of acetate solutions of other alkali metal ions gave low values for the resting potential and followed the sequence K > Na > Rb > Li > Cs. Also NH 4 and Tris ions gave low values for the resting potential which underwent oscillations associated with the twitching of the fibre and occasionally became positive in value (action potential). 5. Addition of tetraethyl ammonium chloride (TEA‐Cl), 20–100 m M , to K acetate solutions (200 m M ) depolarized the fibre membrane and the consequent reduction of resting potential varied linearly with the logarithm of TEA concentration. 6. Replacement of chloride ion by acetate or isethionate in the external solution did not change significantly the resting potential although the values were consistently lower by about 2 mV. 7. Complete elimination of K in the external solution and reduction of its ionic strength using sucrose depolarized the muscle fibres by about 27 mV when Na was changed from 475 to 1 m M . Under these conditions, external solutions completely in acetate form gave resting potentials which were more positive than those observed in completely chloride solutions by 6–8 mV. 8. Replacement of Na by Li, Tris, choline, tetramethyl or tetraethyl ammonium ion in the external solution made the values of the resting potential more positive (depolarization). Similarly increasing the concentration of K (or Cs or Rb in place of K) by correspondingly decreasing the concentration of Na in the outside solution depolarized the fibres and the resting potential became zero at a concentration of 280 m M (or 308 or 1500 m M for Rb or Cs, respectively) on extrapolation.