Quantitative Model for Ion Transport and Cytoplasm Conductivity of Chinese Hamster Ovary Cells

In mammalian cells cytoplasm ion concentrations and hence cytoplasm conductivity is an important indicator of their physiological state. Changes in the cytoplasm conductivity has been associated with physiological changes such as progression of cancer and apoptosis. In this work, a model that predicts the effects of physiological changes in ion transport on the cytoplasm conductivity of Chinese hamster ovary (CHO) cells is demonstrated. We determined CHO-specific model parameters, Na(+)/K(+) ATPase pumps and ion channels densities, using a flux assay approach. The obtained sodium (P(Na)), potassium (P(K)) and chloride (P(Cl)) permeability and Na(+)/K(+) ATPase pump density were estimated to be 5.6 × 10(−8) cm/s, 5.6 × 10(−8) cm/s, 3.2 × 10(−7) cm/s and 2.56 × 10(−11) mol/cm(2), respectively. The model was tested by comparing the model predictions with the experimentally determined temporal changes in the cytoplasm conductivity of Na(+)/K(+) ATPase pump inhibited CHO cells. Cells’ Na(+)/K(+) ATPase pumps were inhibited using 5 mM Ouabain and the temporal behavior of their cytoplasm conductivity was measured using dielectrophoresis cytometry. The measured results are in close agreement with the model-calculated values. This model will provide insight on the effects of processes such as apoptosis or external media ion concentration on the cytoplasm conductivity of mammalian cells.