"Hypotonic regulation of mouse epithelial sodium channel in Xenopus laevis oocytes", Galizia, Luciano; Marino, Gabriela; Ojea, Alejandro; Kotsias, Basilio.

LUCIANO GALIZIA, GABRIELA I. MARINO, ALEJANDRO OJEA & BASILIO A. KOTSIAS

JOURNAL OF MEMBRANE BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2013 vol. 246 p. 949 - 958

0022-2631

The regulation of the epithelial Na? channel(ENaC) during cell swelling is relevant in cellular pro-cesses in which cell volume changes occur, i.e., migration,proliferation and cell absorption. Its sensitivity to hypo-tonically induced swelling was investigated in the Xenopusoocyte expression system with the injection of the threesubunits of mouse ENaC. We used voltage-clamp tech-niques to study the amiloride-sensitive Na? currents(INa(amil)) and video microscopic methodologies to assessoocyte volume changes. Under conditions of mild swelling(25 % reduced hypotonicity) inward current amplitudedecreased rapidly over 1.5 min. In contrast, there was nochange in current amplitude of H2O-injected oocytes to theosmotic insult. INa(amil) kinetics analysis revealed adecrease in the slower inactivation time constant during thehypotonic stimuli. Currents from ENaC-injected oocyteswere not sensitive to external Cl- reduction. Neither short-nor long-term cytochalasin D treatment affected theobserved response. Oocytes expressing a DEG mutant b-ENaC subunit (b-S518K) with an open probability of 1 hadreduced INa(amil) hypotonic response compared to oocytesinjected with wild-type ENaC subunits. Finally, during thehypotonic response ENaC-injected oocytes did not show acell volume difference compared with water-injectedoocytes. On this basis we suggest that hypotonicity-dependent ENaC inhibition is principally mediated throughan effect on open probability of channels in the membrane.