Plasma membrane potential of Lettré cells does not depend on cation gradients but on pumps.
The plasma membrane potential of Lettré cells has been determined with the optical indicator oxonol-V and found to be -57 mV at 37 degrees C (range -20 to -80 mV depending on the physiological condition of the cells). Increasing extracellular K+ does not depolarize cells: even in the presence of 155 mM K+ the potential is -41 mV; membrane potential is also insensitive to the chemical gradient of Na+, Mg2+, Ca2+ or Cl-. Ouabain depolarizes the cells; H+ efflux from cells is stimulated by extracellular Na+. We propose that in Lettré cells the plasma membrane potential is generated by electrogenic cation pumps. The balancing fluxes of Na+ and K+ are mainly through electroneutral cation exchanges (Na+/K+ and Na+/H+) and the magnitude of the potential is limited by organic anion leaks. Such a mechanism may operate in other biological membranes also.
D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000503:physiopathology*; D002412:Cations; D002462:Cell Membrane / Q000502:physiology; D005456:Fluorescent Dyes; D007555:Isoxazoles; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008954:Models, Biological; D010042:Ouabain / Q000494:pharmacology; D013816:Thermodynamics; D014634:Valinomycin / Q000494:pharmacology
D002412:Cations; D005456:Fluorescent Dyes; D007555:Isoxazoles; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D010042:Ouabain; C013633:oxonol V