Balance of unidirectional monovalent ion fluxes in cells undergoing apoptosis: why does Na+/K+ pump suppression not cause cell swelling?

. 2011 Mar 21;589(Pt 9):2197–2211. doi: 10.1113/jphysiol.2011.207571

Intracellular water and ion content
Water	Cell water (determined in present study by buoyant density) (ml (g protein)⁻¹)
	Na⁺ content (determined in present study by flame photometry) (μmol (g protein)⁻¹)
	K⁺ content (determined in present study by flame photometry) (μmol (g protein)⁻¹)
Cl⁻	Cl⁻ content (determined in present study by the steady-state ³⁶Cl⁻ distribution, specific radioactivity of the extracellular medium and [Cl]_o) (μmol (g protein)⁻¹)
A	‘Impermeant’ osmolytes in cell (μmol (g protein)⁻¹)
	.
Concentration of ions (mM)
[Na]_i, [K]_i, [Cl]_i	Concentration of ions in cell water
[Rb]_I	Intracellular Rb⁺ concentration under the balanced state, [Rb]_i=[K]_i[Rb]_o/[K]_o
[Na]_o, [K]_o, [Cl]_o, [Rb]_o	Concentration of ions in extracellular medium
Potentials
u	Membrane potential (dimensionless) (eqn (A11))
U	Membrane potential U=uRT/F; for 37°C U = 26.7u (mV)
U₀	Membrane potential when NKCC is absent (mV) (eqn (A12))
	‘Equilibrium’ potential for K⁺(Rb⁺), (dimensionless)
	‘Equilibrium’ potential for Cl⁻, (dimensionless)
Kinetic coefficients of ion Cl⁻ exchange and integral channel permeability
k	Rate constant of the total Cl⁻ exchange (determined by ³⁶Cl⁻) (min⁻¹)
P_Na, P_K, P_Cl	Coefficient of integral channel permeability of membrane for Na⁺, K⁺ and Cl⁻ (ml min⁻¹ (g protein)⁻¹) (eqns (A15)–(A17))
Fluxes (μmol min⁻¹ (g protein)⁻¹)
	Total Cl⁻ influx ≡ efflux determined by the kinetic of ³⁶Cl⁻ uptake or release under the balanced distribution of Cl⁻,
	Flux related to the one-for-one Cl⁻ exchanger
	Difference between the measured Cl⁻ flux and the flux related to the one-for-one Cl⁻ exchanger,
	Cl⁻ influx through electroconductive Cl⁻ channels (eqn (A13))
	Cl⁻ efflux through electroconductive Cl⁻ channels (eqn (A14))
	Cl⁻ influx via NKCC pathway (eqn (A6))
	Cl⁻ efflux via NKCC pathway,
	Half the Cl⁻ influx and the whole Na⁺ or K⁺ influxes via NKCC pathway
	Half the Cl⁻ efflux and the whole Na⁺ or K⁺ effluxes via NKCC pathway,

	Influx Na⁺ and Cl⁻ via NC cotransport =, calculated by eqn (A4)
	Efflux of Na⁺ and Cl⁻ via NC cotransport,
	‘Pump’ Na⁺ efflux,
	‘Pump’ K⁺ influx
	Total Rb⁺ influx estimated by Rb⁺ flame photometry
	Ouabain-resistant Rb⁺ influx in the presence of ouabain
	Ouabain sensitive, the ‘pump’ Rb⁺ influx,
	Rb⁺ influx through channels
	Rb⁺ efflux through channels
	Ratio between efflux and influx via cotransporters NKCC or, respectively, NC (eqns (A2.1) and (A2.2))