Amino acid transport and cell volume regulation in Ehrlich ascites tumour cells.

Abstract

SUMMARY1. Cellular and extracellular concentrations of amino acids were measured in Ehrlich ascites cells by amino acid analysis and by distribution of radioactive amino acids between cells and medium. Dilution of the medium results in a reduction in the cellular concentration of non-essential amino acids and taurine and an equivalent increase in the extracellular content of these amino acids.2. The membrane potential and the electrochemical gradient of sodium were measured. The decrease in the cellular to extracellular gradient of taurine and glycine is not a consequence of a decrease in the sodium gradient but is caused by the changes in osmolarity and cell volume.3. The unidirectional influx and efflux of glycine and taurine were measured as the initial flux of [14C]glycine and [35S]taurine, using a rapid filter technique. For both amino acids the rate constants for influx are decreased and the rate constants for efflux increased following a reduction in osmolarity.4. The taurine and glycine fluxes were analysed as a simple pump and leak system. Reduction in osmolarity increases the leak permeability to both taurine and glycine.5. The results for glycine are also discussed in relation to a Na+-glycine co-transport model, where reduction in osmolarity increases the leak permeability to glycine.6. The cellular permeability to taurine and glycine increases as a function of increasing cell volume. The taurine permeability increases 7-fold and the glycine permeability 1-5-fold with an increase in cell volume of 30 %. The absolute increase in permeability is equal for both taurine and glycine.

Effects of hyposmotic shock on taurine transport in isolated trout hepatocytes

“…Owing to their different ionic relationships the uptake and efflux of taurine are not symmetrical. It is usually observed that RVD is associated with stimulation of the Na+-independent efflux of taurine, while the Na+-dependent influx is actually diminished (Hoffmann & Lambert, 1983;Fugelli & Thoroed, 1986;Fincham et al 1987). Fish erythrocytes differ from other cells in that hyposmolarity activates not only the output but also the uptake of taurine via a sodium-independent mechanism (Fugelli & Thoroed, 1986;Fincham et al 1987).…”

“…This contribution has been described in invertebrates and also in mammalian tissues such as cardiac cells (Thurston, Hauhart & Naccarato, 1981), Ehrlich cells (Hoffmann & Lambert, 1983;Lambert, 1984;Lambert & Hoffmannn, 1993) (Fugelli & Thoroed, 1986;Kirk, Ellory & Young, 1992), the skate (Goldstein & Brill, 1990, the eel (Fincham, Wolowyk & Young, 1987) and the trout (Garcia-Romeu, Cossins & Motais, 1991), and also in the cyclostomes, hagfish and lamprey (Brill, Musch & Goldstein, 1992).…”

Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

“…EATC and the retina, 84,85 which reflects a low plasma membrane permeability to the zwitter-ionic taurine (high water solubility/low lipophilicity) and the presence of a Na C -dependent, high-affinity transporter TauT (SLC6A6) in the plasma membrane. 13 However, it has been demonstrated that following osmotic cell swelling in e.g., EATC 84 and NIH3T3 mouse fibroblasts 86,87 a net loss of taurine and hence restoration of cell volume are partly ensured by activation of a volume-sensitive leak pathway for organic osmolytes, designated VSOAC (volume sensitive organic anion channel) and a concomitant down-regulation of TauT. Using HeLa cells (Fig.…”

The effect of a hyposmotic shock on amino acid efflux from lactating rat mammary tissue: stimulation of taurine and glycine efflux via a pathway distinct from anion exchange and volume‐activated anion channels

“…see Fincham, Wolowyk & Young, 1987;Goldstein & Brill, 1990). Indeed, taurine and other amino acids, notably glycine and alanine, have been shown to contribute to a RVD in some mammalian cells, such as Ehrlich ascites tumour cells and rat heart (Thurston, Hauhart & Naccarato, 1981;Hoffmann & Lambert, 1983).…”