title: The measurement of intracellular sodium ion concentration in the horizontal cells of the stingray retina.
abstract: Membrane potentials, and intracellular concentrations of sodium ions in the horizontal cells of the stingray retina were measured directly by means of ion-selective microelectrodes. The electrodes used were of the double-barreled type and bis[(12-crown-4)methyl]methyldodecylmalonate was used as the ion-selective resin. The average intracellular concentration of Na+ ions in the horizontal cells and the extracellular concentration of Na+ ions near the horizontal cells were 123 mM and 351 mM, respectively (n = 27). The equilibrium potential was estimated to be +27.3 mV. Although each value of the equilibrium potential was scattered over a wide range, they were always positive regardless of the membrane potential. This was the first direct measurement of the sodium ion-concentration for the retinal horizontal cells. The results support the idea that the origin of the dark depolarization of the stingray horizontal cell is caused by the glutamate-induced high-sodium conductance of the membrane.
authors.affiliation: Department of Biological Science, Faculty of Science, Hiroshima University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Fujimoto
authors.forename: J
authors.initials: J
authors.lastname: Katayama
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D008564:Membrane Potentials; D010775:Photic Stimulation; D012160:Retina / Q000737:chemistry* / Q000502:physiology; D012860:Skates, Fish; D012964:Sodium / Q000032:analysis*
chemical_list: D012964:Sodium