title: A mutant of Paramecium with increased relative resting potassium permeability.
abstract: Fast-2, a membrane mutant of Paramecium aurelia, is due to a single-gene mutation and has behavioral abnormalities. Intracellular recordings through changes of external solutions were made. The mutant membrane hyperpolarized when it encountered solutions with low K+ concentration. This hyperpolarization and other associated activities were best observed in Ca- or Na-solutions devoid of K+. Membrane potential was plotted against the concentration of K+ (0.5 to 16 mM) in solutions of fixed Na+ or Ca++ concentration. The slopes of the curves for the mutant membrane were steeper than those for the wild type at the lower concentrations of K+. Inclusion of 2 mM tetraethylammonium chloride (TEA-Cl) counteracted the mutational effects. Spontaneous action potentials in Ba-solution and the electrically evoked action potentials in various solutions are normal in this mutant. We conclude that the resting permeability to K+ relative to the permeabilities to Na+ and Ca++ has been increased by the mutation.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004553:Electric Conductivity; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009154:Mutation; D010247:Paramecium / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D013757:Tetraethylammonium Compounds; D001464:Barium; D012964:Sodium; D011188:Potassium; D002118:Calcium