COMPUTATION OF THE K+, Na+ AND Cl– FLUXES THROUGH PLASMA MEMBRANE OF ANIMAL
CELL WITH Na+/K+ PUMP, NKCC, NC COTRANSPORTERS, AND IONIC CHANNELS
WITH AND WITHOUT NON-GOLDMAN RECTIFICATION IN K+ CHANNELS. NORMA AND APOPTOSIS
A. A. Rubashkin, V. E. Yurinskaya, A. A. Vereninov 1
Institute of Cytology RAS, St. Petersburg;
1 e-mail: verenino@mail.ru
The balance of K+, Na+ and Cl– fluxes through cell membrane with the Na+/K+ pump, ion channels and
NKCC and NC cotransporters is considered. It is shown that all unidirectional K+, Na+ and Cl– fluxes through
cell membrane, permeability coefficients of ion channels and membrane potential can be computed for balanced
ion distribution between cell and the medium if K+, Na+ and Cl– concentration in cell water and three fluxes are
known: total Cl– flux, total K+ influx and ouabain-inhibitable «pump» component of the K+ influx. Changes in
the mortovalent ion balance in lymphoid cells U937 induced to apoptosis by 1 μM staurosporine are analyzed as
an example. It is found that the apoptotic shift in ion and water balance in studied cells is caused by a decrease in
the pump activity which is accompanied by a decrease in the integral permeability of Na+ channels without significant
increase in K+ and Cl– channel permeabilities. Computation shows that only a small part of the total fluxes
of K+, Na+ and Cl– accounts for the fluxes via NKCC and NC cotransporters. Therefore, cotransport fluxes
can not be studied using inhibitors.
Key words: cell ion and water balance, apoptosis, ion channels, ion transporters, Cl– fluxes
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