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R Sánchez Olea

Publications and source records attributed to R Sánchez Olea.

9 recordsLinked to original sources
PubMed1997

Volume regulation in NIH/3T3 cells not expressing P-glycoprotein. I. Regulatory volume decrease.

Exposure of NIH/3T3 fibroblasts not expressing P-glycoprotein to 50, 30, 20, and 10% hyposmotic solutions led to cell volume increases of 70, 32, 21, and 12%, respectively. After swelling, NIH/3T3 cells exhibited regulatory volume decrease (RVD), attaining complete volume recovery after 30 min except in 50% hyposmotic solution, in which volume recovery was 76%. RVD was accelerated by gramicidin and inhibited by the Cl channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoic acid, 1,9-dideoxyforskolin, dipyridamole, and niflumic acid and by the K channel, blocker quinidine. RVD was reduced 15% by removal of extracellular Ca. The pathway opened by hypotonicity was highly permeable to K and Rb and only partly permeable to other cations. Most anions were able to permeate, with a permeability ranking of nitrate > benzoate = iodide > thiocyanate > chloride > > gluconate. The pathway was permeable to neutral amino acids, with a permeability ranking of glycine > alanine > glutamate > taurine > gamma-aminobutyric acid > glutamine. The pathway was not permeable to basic amino acids. These results show that, despite the absence of P-glycoprotein, NIH/3T3 cells exhibit RVD with properties similar to those expressed in most cell types.

3T3 Cells↗
PubMed1993

Contribution of organic and inorganic osmolytes to volume regulation in rat brain cells in culture.

In this work we examined the time course and the amount released, by hyposmolarity, for the most abundant free amino acids (FAA) in rat brain cortex astrocytes and neurons in culture. The aim was to evaluate their contribution to the process of cell volume regulation. Taurine, glutamate, and D-aspartate in the two types of cells, beta-alanine in astrocytes and GABA in neurons were promptly released by hyposmolarity, reaching a maximum within 1-2 min. after an osmolarity change. A substantial amount of the intracellular pool of these amino acids was mobilized in response to hyposmolarity. The amount released in media with osmolarity reduced from 300 mOsm to 150 mOsm or 210 mOsm, represented 50%-65% and 13%-31%, respectively, of the total amino acid content in cells. In both astrocytes and neurons, the efflux of glutamine and alanine was higher under isosmotic conditions and increased only marginally during hyposmotic conditions. 86Rb+, used as tracer for K+, was released from astrocytes, 30% and 11%, respectively, in hyposmotic media of 150 mOsm or 210 mOsm but was not transported in neurons. From these results it was calculated that FAA contribute 54% and inorganic ions 46% to the process of volume regulation in astrocytes exposed to a 150 mOsm hyposmotic medium. This contribution was 55% for FAA and 45% for K+ and Cl- in cells exposed to 210 mOsm hyposmotic solutions. These results indicate that the contribution of FAA to the process of cell volume regulation is higher in astrocytes than in other cell types including renal and blood cells.

Amino Acids↗
PubMed1991

Taurine release associated to volume regulation in rabbit lymphocytes.

Rabbit lymphocytes exposed to hyposmotic media first swell and then recover their initial volume within 6 min. During volume recovery, free amino acids (FAA) decrease from 451.1 to 208 nmoles/mg protein. Taurine was the dominating FAA, accounting for 70% of the FAA pool. The time course of 3H-taurine release induced by hyposmolarity followed that of volume recovery. Efflux of 3H-taurine in an 8 min period was 17.8% (of total labeled taurine accumulated during loading) in an isosmotic medium. Reducing osmolarity to 0.87, 0.75, 0.62, and 0.5 increased this release to 24.8%, 38.1%, 56.4% and 70.9%, respectively. The volume-sensitive release of 3H-taurine was unaffected by omission of external Na+ or Ca++ and was reduced by 23% in the absence of Cl-. It was unaffected by agents disrupting the cytoskeleton or by tetraethylammonium, barium, quinidine, and gadolinium, but was 26% reduced by DIDS. Taurine release was inhibited at 4 degrees C, but was unchanged at 15 degrees C or 25 degrees C. An involvement of FAA, particularly taurine, in lymphocyte volume regulation is suggested.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

Hyposmolarity-induced taurine release in cerebellar granule cells is associated with diffusion and not with high-affinity transport.

The effects of hyposmotic conditions on taurine uptake and release were studied in mice cultured cerebellar granule cells. The effect of DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonate) and of the divalent cations Mg++ and Mn++ on the hyposmolarity-induced changes in these parameters was investigated. Mg++ (20 mM) and Mn++ (5 mM) inhibited by 25% and 41%, respectively, the release of taurine observed in 30% hyposmolar media. DIDS (100 microM) inhibited this release by 46%. Taurine efflux evoked by 50% hyposmolar solutions was reduced about 40% by Mg++ and 55% by Mn++. Taurine uptake into the granule cells could be resolved into a high-affinity carrier-mediated component plus a nonsaturable diffusion component. The kinetic constants (Km and Vmax) for the high-affinity uptake were unaffected by a 50% decrease in the osmolarity. The diffusion constant for the nonsaturable taurine uptake was increased from 1.5 x 10(-4) in isosmotic media to 4.6 x 10(-4) ml x min-1 x mg-1 in hyposmotic (50%) media. This increase in the diffusional component of taurine uptake elicited by the hyposmotic condition was inhibited approximately 25% by either 100 microM DIDS or 5 mM Mn++. These results strongly suggest that the increase in taurine release induced by swelling under hyposmotic conditions is mediated by a diffusional process and not by a reversal of the high-affinity taurine carrier.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

Osmolarity-sensitive release of free amino acids from cultured kidney cells (MDCK).

The amino acid pool of MDCK cells was essentially constituted by alanine, glycine, glutamic acid, serine, taurine, lysine, beta-alanine and glutamine. Upon reductions in osmolarity, free amino acids were rapidly mobilized. In 50% hyposmotic solutions, the intracellular content of free amino acids decreased from 69 to 25 mM. Glutamic acid, taurine and beta-alanine were the most sensitive to hyposmolarity, followed by glycine, alanine and serine, whereas isoleucine, phenylalanine and valine were only weakly reactive. The properties of this osmolarity-sensitive release of amino acids were examined using 3H-taurine. Decreasing osmolarity to 85, 75 or 50% increased taurine efflux from 0.6% per min to 1.6, 3.5 and 5.06 per min, respectively. The time course of 3H-taurine release closely follows that of the regulatory volume decrease in MDCK cells. Taurine release was unaffected by removal of Na+, Cl- or Ca2+, or by treating cells with colchicine or cytochalasin. It was temperature dependent and decreased at low pH. Taurine release was unaffected by bumetanide (an inhibitor of the Na+/K+/2Cl- carrier); it was inhibited 16 and 67 by TEA and quinidine (inhibitors of K+ conductances), unaffected by gadolinium or diphenylamine-2-carboxylate (inhibitors of Cl- channels) and inhibited 50% by DIDS. The inhibitory effects of DIDS and quinidine were additive. Quinidine but not DIDS inhibited taurine uptake by MDCK cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1990

Chloride dependence of the K(+)-stimulated release of taurine from synaptosomes.

Exposure of a crude synaptosomal fraction to K+ concentrations ranging from 25 to 100 mM evokes the release of [3H]taurine and [3H]GABA. These high concentrations of K+ induce, besides depolarization, a marked synaptosomal swelling, which is prevented by replacing chloride in the solutions with the largely impermeant anion gluconate. The depolarizing effect of K+ is unaffected by omission of chloride. The K(+)-evoked release of taurine seems related to K(+)-induced changes in synaptosomal volume rather than to a depolarizing effect, since it is totally calcium-independent but is abolished by reducing chloride and by making solutions hypertonic with mannitol. The release of [3H]GABA, in contrast is unaffected in chloride-free or hypertonic solutions.

Animals↗