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Effect of hyperosmolar medium on living U937 cell. (A-C) cell water content, (D-F) intracellular K + , Na + content, (G-I) ouabain-sensitive (OR) and -resistant (OR) Rb + influxes, (J -L) Na + concentrations and beta, (M) the percentage of cells with RVI (fraction L) after 2-hour and 4-hour incubation in a hypertonic medium assessed by protein, (N, O) DMA+DIDS (DD) effect on RVI in hyperosmolar medium with 150 mM sucrose. Solid lines with open
Source publication
The work provides a modern mathematical description of animal cell electrochemical system under a balanced state and during the transition caused by an increase in external osmolarity, considering all the main ionic pathways in the cell membrane: the sodium pump, K+, Na+, Cl- electroconductive channels and cotransporters NC, KC, and NKCC. The descr...
Contexts in source publication
Context 1
... is the AVD associated with apoptosis ( Okada et al., 2001), and the oppositely directed RVI, which precedes the AVD ( Yurinskaya et al., 2012). In our experience, the analysis of the distribution of cells in the density gradient is the best method for separating the primary rapid physical decrease in the volume of cells in the hyperosmolar environment and the specific processes of RVI and AVD (Figure 6). Due to the time shift, RVI and AVD can be observed on the same sample of cells. ...
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... essential detail is that the transition from RVI to AVD in the cell population manifests itself as a change in the ratio between the number of cells in the RVI and AVD stages. The number of RVI cells decreases over time and the number of AVD cells increases ( Figure 6M). This indicates that the transition from RVI to AVD in each cell is fast. ...
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... RVI and AVD mechanisms are discussed in more detail below, considering computer simulations of the system and data related to U937 cells (Yurinskaya et al., 2011(Yurinskaya et al., , 2012(Yurinskaya et al., , 2017. In the experiments shown in Figure 6, the mean values of ions and water during the first 2 hours characterize mainly cells at the RVI stage. At the time point 4 h the light, RVI, and heavy, AVD, subpopulations could be analyzed separately. ...
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... should be associated with an increase in the intracellular content of Na + and Cl -and a slight change in the content of K + . It is these changes in the content of Na + and K + that were observed in experiments with U937 cells for a light subpopulation of RVI in a hyperosmolar medium with sucrose ( Figure 6E, Table 6). The key role of the NC cotransporter in RVI is independently confirmed by the blocking effect of the combination of dimethylamiloride, a known inhibitor of Na/H exchanger, and DIDS, which inhibits the Cl/HCO3 exchanger ( Figure 6N, O). ...
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... is these changes in the content of Na + and K + that were observed in experiments with U937 cells for a light subpopulation of RVI in a hyperosmolar medium with sucrose ( Figure 6E, Table 6). The key role of the NC cotransporter in RVI is independently confirmed by the blocking effect of the combination of dimethylamiloride, a known inhibitor of Na/H exchanger, and DIDS, which inhibits the Cl/HCO3 exchanger ( Figure 6N, O). In hyperosmolar medium with addition NaCl an increase in inc or a decrease in ikc, inkcc, pCl or appearance of channels HICC increases RVI (Figures 3E, O, 4A, I, Table 5). ...
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... all these cases, RVI is associated with an increase in the total content of K + and Na + , but the relative changes in the content of K + and Na + depend on which parameter changes. (Figure 6A, D). However, the available data are insufficient to differentiate the mechanism of RVI in these cases in more detail. ...
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... experiments where cells U937, K562, and Jurkat were studied in parallel in hyperosmolar medium with 200 mM sucrose for 4 h the certain differences between cell species were revealed (Table 6, Figure 7). RVI at the time point 4 h was rather small but differences in K + and Na + content in K562, Jurkat and U937 cells were significant. ...
Citations
... Our thanks to Igor Raikov, a student of the Alferov Federal State Academic University RAS, Russia, for checking the use of the BEZ02BC file on a 32-bit computer. This manuscript has been released as a Pre-Print at BioRxiv, online Nov. 15, 2021 (Yurinskaya and Vereninov, 2021b). ...
Studying the transport of monovalent ions across the cell membrane in living cells is complicated by the strong interdependence of fluxes through parallel pathways and requires therefore computational analysis of the entire electrochemical system of the cell. Current paper shows how to calculate changes in the cell water balance and ion fluxes caused by changes in the membrane channels and transporters during a normal regulatory increase in cell volume in response to osmotic cell shrinkage (RVI) followed by a decrease in cell volume associated with apoptosis (AVD). Our recently developed software is used as a computational analysis tool and the established human lymphoid cells U937 are taken as an example of proliferating animal cells. It is found that, in contrast to countless statements in the literature that cell volume restoration requires the activation of certain ion channels and transporters, the cellular responses such as RVI and AVD can occur in an electrochemical system like U937 cells without any changes in the state of membrane channels or transporters. These responses depend on the types of chloride cotransporters in the membrane and differ in a hyperosmolar medium with additional sucrose and in a medium with additional NaCl. This finding is essential for the identification of the true changes in membrane channels and transporters responsible for RVI and AVD in living cells. It is determined which changes in membrane parameters predicted by computational analysis are consistent with experimental data obtained on living human lymphoid cells U937, Jurkat, and K562 and which are not. An essential part of the results is the developed software that allows researchers without programming experience to calculate the fluxes of monovalent ions via the main transmembrane pathways and electrochemical gradients that move ions across the membrane. The software is available for download. It is useful for studying the functional expression of the channels and transporters in living cells and understanding how the cell electrochemical system works.
