The logic of ionic homeostasis: Cations are for voltage, but not for volume - Fig 7

Changes of intracellular ionic concentrations (A, C), Emand the cell volume (B, D) evoked by temporary reduction of Na+conductance. A: Changes of [Na+]i, [K+]i, and [Cl-]i, after reduction of gNa to 2*109 ions/(sec*V) for 10 seconds starting at time = 0 (grey area) and then returning to the original gNa of 8*109 ions/(sec*V) for the next 10 seconds; gCl = 1010 (solid lines) and 1*108 ions/(sec*V) (dashed lines); imaginary electroneutral 3Na+/3K+-pump, activity of 2.41*108 ATP/sec. B: Changes of the cell volume (scale on the left, in % of original volume) and voltage (scale on the right) with the same temporary reduction of gNa; the lines are as in part A. C: and D: the same as parts A and B, respectively, but with an electrogenic 3Na+/2K+-pump, activity 2.72*108 ATP/sec. All simulations were in “realistic” conditions. Initial conditions (A-D): [Na+]o = 145 mM; [K+]o = 5 mM; [Cl-]o = 150 mM; [neutral osmolyte]o = 6 mM; gNa = 8*109 ions/(sec*V); gK = 1.2*1010 ions/(sec*V); (A, B): [Na+]i = 16.3 mM; [K+]i, = 158.3 mM; [Cl-]i = 45.3 mM; [An-]i = 86.2 mM; z = -1.5; 3Na+/3K+ pump; (C, D): [Na+]i = 18.5 mM; [K+]i = 160.0 mM; [Cl-]i = 25.7 mM; [An-]i = 101.9 mM; z = -1.5; 3Na+/2K+ pump. Changes at time = 0 (A-D): gNa = 2*109 ions/(sec*V); Changes at time = 10 sec (A-D): gNa = 8*109 ions/(sec*V).