Hyponatremia alters the biophysical properties of neuronal cells independently of osmolarity: a study on Ni(2+) -sensitive current involvement

Hyponatremia is the most frequent electrolyte disorder encountered in hospitalized patients and it can cause a wide variety of neurological symptoms. Most of the negative effects of this condition on neuronal cells are due to cell swelling following the reduction of plasma osmolarity, although in hyponatremia different membrane proteins are supposed to be involved in the conservation of neuronal volume. We have recently reported detrimental effects of hyponatremia on two different neuronal cell lines, SK-N-AS and SH-SY5Y, independent of osmotic alterations. Here we aimed to study, in the same cell lines, whether hyponatremic condition can per se cause electrophysiological alterations and if these effects vary over time. Accordingly, we made experiments in low sodium medium either in hypo-, Osm(-), or iso-osmotic condition, Osm(+), for a short (24 h) or long time (7 d). By a patch pipette in voltage clamp condition, we recorded possible modifications of cell capacitance, Cm , and membrane conductance, Gm . Our results indicate that both Osm(-) or Osm(+) medium, Cm and Gm show a similar increase but such effects are differently dependent on time in culture. Notably, regarding to the possibly involved mechanisms for the maintenance of Cm , Gm and Gm /Cm in Osm(+) condition, we observed a greater contribution of Na(+) /Ca(2+) exchanger respect to Osm(-) and control. Overall, these novel electrophysiological results help us understand the mechanisms of volume regulation following ionic perturbation. Our results can also have relevance in a translational perspective because the Na(+) /Ca(2+) exchanger can be considered a target for planning novel therapies. This article is protected by copyright. All rights reserved.