Dexamethasone increases fluid absorption via Na+/H+ exchanger (NHE) 3 activation in normal human middle ear epithelial cells

Activation of epithelial sodium channel in human middle ear epithelial cells by dexamethasone

“…1A). As previously reported (Choi et al, 2006a), the apical addition of amiloride (100 μM) produced a rapid decrease of current due to the blockage of ENaC. The mean amplitude of the amiloride-sensitive current, which reflects ENaC activity, was 13.92 ± 1.39 μA/cm 2 (n = 3) in NHMEE cells, which is comparable to the previous measurements (Choi et al, 2006a).…”

“…As previously reported (Choi et al, 2006a), the apical addition of amiloride (100 μM) produced a rapid decrease of current due to the blockage of ENaC. The mean amplitude of the amiloride-sensitive current, which reflects ENaC activity, was 13.92 ± 1.39 μA/cm 2 (n = 3) in NHMEE cells, which is comparable to the previous measurements (Choi et al, 2006a). After 12-h incubation with dexamethasone (10 − 7 M), the mean amplitude of the amiloride-sensitive current was greatly increased to 23.67 ±2.11 μA/cm 2 (P b 0.5, n = 3) In contrast, forskolin-induced Isc was not changed after dexamethasone treatment (control; 3.87 ± 0.61 μA/cm 2 , dexamethasone treatment; 4.43 ± 0.97 μA/cm 2 ( Fig.…”

“…Interestingly, the middle ear epithelium, which is considered extension of respiratory epithelium, shows some distinct characteristics in ion transport mechanisms. Amiloride-sensitive transepithelial current is enhanced in the middle ear epithelial cells, suggesting that fluid absorption appears to be more dependent on ENaC in the middle ear epithelial cells than in other airway epithelia (Choi et al, 2006a). The increased activity of ENaC in the middle ear is thought to contribute to maintaining a relatively thinner ASL and keeping the middle ear cavity fluid-free.…”

“…Epithelial Na + channel (ENaC) is expressed in the apical surface of various absorptive epithelia including tracheobronchial and alveolar epithelia, where it functions as major determinant of Na + and fluid absorption (Alvarez et al, 2000). Studies have also revealed that the middle ear epithelial cells also express ENaC which has a critical role in fluid absorption (Choi et al, 2006a;Yen et al, 1993;Herman et al, 1992;DeSerres et al, 1991). ENaC has been demonstrated to be the major determinant of baseline electrogenic ion transport in Mongolian gerbil middle ear epithelium (Herman et al, 1992 ;Herman et al, 1993) and cultured human middle ear epithelial cells (Choi et al, 2006a).…”

Dexamethasone acutely accelerates pleural fluid absorption in mice hydrothoraces

“…/H ? exchanger) [7][8][9][10][11], which, in turn, have been implicated in pleural fluid absorption [12,13]. We thus hypothesized that corticosteroids increase the absorption rate of isosmotic hydrothoraces in mice.…”