Analysis of the monovalent ion fluxes in U937 cells under the balanced ion distribution: recognition of ion transporters responsible for changes in cell ion and water balance during apoptosis.

Unidirectional (22)Na, Li(+) and Rb(+) fluxes and net fluxes of Na(+) and K(+) were measured in U937 human leukemic cells before and after induction of apoptosis by staurosporine (1 microM, 4 h) to answer the question which ion transporter(s) are responsible for changes in cell ion and water balance at apoptosis. The original version of the mathematical model of cell ion and water balance was used for analysis of the unidirectional ion fluxes under the balanced distribution of major monovalent ions across the cell membrane. The values of all major components of the Na(+) and K(+) efflux and influx, i.e. fluxes via the Na(+),K(+)-ATPase pump, Na(+) channels, K(+) channels, Na/Na exchanger and Na-Cl symport were determined. It is concluded that apoptotic cell shrinkage and changes in Na(+) and K(+) fluxes typical of apoptosis in U937 cells induced by staurosporine are caused by a complex decrease in the pump activity, Na-Cl symport and integral Na(+) channel permeability.

Differential transcription of ion transporters, NHE1, ATP1B1, NKCC1 in human peripheral blood lymphocytes activated to proliferation.

This work, using RT PCR, studied expression of mRNAs encoding ion transporters, the Na/H antiporter (NHE1), the beta subunit of the Na,K-ATPase pump (ATP1B1), the NaK2Cl symporter (NKCC1), and some proteins unrelated to ion transport: the serum and glucocorticoid dependent kinase (hSGK), beta-actin, a glycolytic enzyme (GAPDH), and regulators of proliferation and apoptosis (p53, Bcl-2) during activation of human lymphocytes with phytohemagglutinin for 4-24 h. Within 24 hours the mRNA levels of NHE1, beta-actin, Bcl-2, and p53 increased by more than 100%, the mRNA levels of ATP1B1, GAPDH, and hSGK, by about 50%, while the mRNA levels of NKCC1 decreased transiently. These results indicate a differential transcriptional control of NHE1, ATP1B1, and NKCC1 following a proliferative stimulus of human lymphocytes.