Enhanced epithelial Na+ channel (ENaC) activity in mouse endometrial epithelium by upregulation of gamma ENaC subunit

The amiloride-sensitive epithelia[ Na+ channel (ENaC), which is made of thr ee different but homologous subunits, controls the rate of transepithelial Na+ absorption in a variety of epithelia. The present study investigated th e functional role of its subunits in regulating ENaC activity, measured as amiloride sensitive short-circuit current (I-SC), in the mouse endometrial epithelium under different culture conditions. The treatment of the culture d epithelia with aldosterone (1 muM) or culturing cells on filters coated w ith concentrated Matrigel resulted in an increase in the amiloride-sensitiv e I-SC. Semiquantitative RT-PCR demonstrated that the expression of alpha a nd beta subunits was not significantly altered by these treatments, but an increase in the gamma subunit expression was observed. An 11-fold increase, induced by aldosterone, in the expression of the gamma subunit, but not in the alpha and beta subunits, was confirmed by capillary electrophoresis wi th laser-induced fluorescence (CE-LIF). The treatment of endometrial cells with antisense against the gamma ENaC subunit abolished the aldosterone-enh anced amiloride-sensitive I-SC. The results indicated an important role of gamma ENaC subunit in determining ENaC activity, and a possible role of the gamma ENaC subunit in interacting with CFTR was also discussed.