Volume regulation in NIH/3T3 cells not expressing P-glycoprotein. II. Chloride and amino acid fluxes

Abstract

The osmolyte function of amino acids and Cl in native NIH/3T3 cells not expressing the P-glycoprotein was examined by investigating the free amino acid concentration and the swelling-activated efflux of [3H]taurine, as representative of amino acids, and of 125I, as a tracer for Cl. Taurine and 125I efflux was activated by 20 and 30% hyposmotic solutions. At 50% hyposmotic solutions, the osmolyte pool was essentially depleted. The Cl channel blockers 5-nitro-2-(3-phenylpropyl-amino)benzoic acid, 1,9-dideoxyforskolin, dipyridamole, and niflumic acid inhibited the release of the two osmolytes by 80-95%. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (400 microM) decreased the efflux of taurine 80% without affecting that of 125I. Linolenic and arachidonic acids (5-20 microM) showed a concentration-dependent inhibitory effect on taurine and 125I fluxes. Omission of Ca decreased osmolyte fluxes by 16%. Verapamil inhibited the osmolyte release only at 500 microM. Nimodipine at 25 and 50 microM decreased the release of [3H]taurine and 125I by approximately 60 and 80%, respectively, but this effect was independent of the presence of extracellular Ca. These results indicate that amino acids and Cl function as osmolytes during regulatory volume decrease in native NIH/ 3T3 cells.

Acquired cisplatin resistance in human ovarian A2780 cancer cells correlates with shift in taurine homeostasis and ability to volume regulate

“…59, 61) and NIH3T3 fibroblasts (0.025-0.055 mol/mg protein; Refs. 42,63). With the use of average values for cellular water and protein content, i.e., 3.24 ml cell water/g cell dry wt (18) and 0.78 g protein/g cell dry wt (15), the taurine content in A2780 cells corresponds to a cellular taurine concentration at 4.5 Ϯ 0.7 mM.…”

Apoptosis to necrosis switching downstream of apoptosome formation requires inhibition of both glycolysis and oxidative phosphorylation in a BCL-XL- and PKB/AKT-independent fashion

“…[30][31][32] We had observed that ddFSK was able to block late apoptotic events. 24 Here we explain those data through the definition of a novel activity of ddFSK as a cell energy metabolism blocker.…”

Physiology of Cell Volume Regulation in Vertebrates

“…This indicates that the great majority of the taurine and Cl Ϫ efflux are mediated by separate channels and that the taurine channel is different from VRAC. Further support for this view is that: 1) swelling-induced taurine release in the absence of Cl Ϫ channel activity has been demonstrated in Xenopus oocytes (947) and in mammary tissue explants (924); 2) the taurine and anion efflux pathways differ with respect to their time course of activity following hypotonic exposure (672,773,961), 3) the two pathways have different sensitivity towards DIDS and arachidonic acid (192,499,672) (for EAT cells see Table 6), and 4) regulation by RhoA (786). It is noted that, in fact, the taurine leak pathway accounts for 5% of the total g Cl in EAT cells (50% reduction in osmolarity; Ref.…”

“…Released arachidonic acid is in itself a bioactive lipid, which can directly activate transport pathways for, e.g., K ϩ (450, 749) and organic osmolytes (491,868). In contrast, at higher concentrations, arachidonic acid directly inhibits swelling-activated K ϩ , Cl Ϫ , and taurine efflux (316, 489,672,881). Arachidonic acid is also an important regulator of cellular signaling processes.…”