Study of the effect of hypotonic stimuli on the mouse epithelial sodium channel (ENaC) activity expressed in Xenopus laevis oocytes: role of the intracellular sodium concentration.

GALIZIA L; MARINO G; PALMA A; KOTSIAS BA

Bahia Blanca

Congreso; Reunión Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

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) [1]. 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 under low intracellular sodium conditions, showed no significative reduction of INa(amil) inward currents measured at -100 mV (INa(amil)ISO : -5.15 ± 0.84 µA vs INa(amil)HIPO :-4.20 ± 0.48 µA, NS, n = 6 ). Moreover, the high intracellular sodium condition elicited an inhibitory response of INa(amil). 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.