Role of the intracellular sodium concentration on the effect of hypotonic shock on the epithelial sodium channel (ENaC).

GALIZIA L; MARINO, G; PALMA, A; KOTSIAS, BA

Congreso; Crosstalk in biophysics and physiology - XLIV Reunion anual de la sociedad Argentina de Biofísica; 2015

The regulation of the epithelial Na+ channel (ENaC) during cell volume increase is relevant in cellular processes involving osmotic challenges. ENaC function is affected by changes of the intracellular sodium concentration. Its sensitivity to hypotonic-induced swelling was investigated in the Xenopus oocyte expression system with the injection of the three subunits of the mouse ENaC (mENaC). We used the voltage clamp technique to measure the amiloride-sensitive Na+ currents (INa(amil)) in order to study the role of intracellular sodium on the ENaC regulation mediated by hyposmotic challenges. ENaC-injected oocytes different intracellular sodium conditions, showed a significative reduction of INa(amil) inward currents from 10 mM to 40 mM. However inactivation of the currents at hyperpolarized pulses increases in that range. Oocytes expressing a DEG mutant of the β-ENaC subunit (β-S518K), which produce an open probability equal to 1 showed a reduced INa(amil) hypotonic mediated inhibitory response in both conditions of intracellular sodium concentration. Based on these results, we suggest that hypotonicity-dependent ENaC inhibition, due to open probability changes is mediated by an intracellular sodium dependent mechanism, probably trough a voltage dependent inactivation effect.