Computation of pump-leak flux balance in animal cells

Many vital processes in animal cells depend on monovalent ion transport across the plasma membrane via specific pathways. Their operation is described by a set of nonlinear and transcendental equations that cannot be solved analytically. Previous computations had been optimized for certain cell types and included parameters whose experimental determination can be challenging.

We have developed a simpler and a more universal computational approach by using fewer kinetic parameters derived from the data related to cell balanced state. A file is provided for calculating unidirectional Na(+), K(+), and Cl(-) fluxes via all major pathways (i.e. the Na/K pump, Na(+), K(+), Cl(-) channels, and NKCC, KC and NC cotransporters) under a balanced state and during transient processes.

The data on the Na(+), K(+), and Cl(-) distribution and the pump flux of K(+) (Rb(+)) are obtained on U937 cells before and after inhibiting the pump with ouabain. There was a good match between the results of calculations and the experimentally measured dynamics of ion redistribution caused by blocking the pump.

The presented approach can serve as an effective tool for analyzing monovalent ion transport in the whole cell, determination of the rate coefficients for ion transfer via major pathways and studying their alteration under various conditions.