Figure 4. H₂S decreases Na⁺/K⁺-ATPase currents of Xenopus lung epithelia.

A) Representative current trace of a control recording. The apical membrane of the lung epithelium was permeabilized with nystatin (100 µM, apical) in the presence of amiloride (10 µM). This resulted in a current increase. When the current was stable, the Na⁺/K⁺-ATPase inhibitor ouabain (1 mM) was applied to the basolateral side. The ouabain-sensitive current fraction (ΔI_ouab) represents the activity of the Na⁺/K⁺-ATPase. B) After permeabilisation with nystatin, NaHS (1 mM) was applied to the apical bath. I_SC decreased significantly from 20.83±3.99 µA/cm² to 16.17±5.23 µA/cm² (n = 6, N = 6, p≤0.05). Subsequently, ouabain-sensitive current fractions were determined. C) Statistical evaluation of experiments as shown in panels A and B. NaHS significantly inhibited Na⁺/K⁺-ATPase activity (ΔI_ouab; n = 6, N = 6, p≤0.05). D) Without permeabilisation with nystatin, ouabain had only a minor effect on transepithelial ion current in the presence of amiloride. Depicted are mean values of non-permeabilized lung epithelia which have been treated with amiloride (10 µM, apical) followed by ouabain (1 mM, basolateral).