Changes in fluid compartments and ionic composition in the isolated chick retina during SD |
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Authors: | F. A. M. De Azeredo H. Martins-Ferreira |
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Affiliation: | (1) Labonatorio de Neuroquimica do Instituto, Biomedico da Universidade Federal Fluminense, Niteroi, RJ, Brasil;(2) Laboratorio de Eletrofisiologia do Instituto de Biofisica da Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil |
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Abstract: | Total content of water, extracellular space (ES), Na+, K+, and Cl– in the isolated chick retina were measured in the presence (test) or absence (control) of spreading depression (SD). During SD in medium with 0.5 mM or 2 mM MgSO4, there is an increase in the intracellular concentration of Na+ and Cl– and a decrease in the intracellular concentration of K+. A decrease in the ES was only found in the medium with 2 mM MgSO4 together with a diminshed outmovement of K+. We suggest that a decrease in the ES is due to an increased absorption of K+ by the Muller cells, causing its swelling and consequently a decrease of the ES.The addition of sucrose (17 mM) to the incubation medium as the extracellular marker markedly decreased the intracellular concentration of Cl– in control retinas, blocked the inward movement of this ion to the tissue during SD and also changed the K+ movement during the phenomenon in medium with 2 mM MgSO4. We suggest that Cl– is an important ion in the ionic balance of the Muller cells and that sucrose must have its site of action that these cells. |
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