H2S does not deplete ATP levels in H441 cells. A: intracellular ATP concentrations of H441 cells, which were exposed to dinitrophenol (DNP, 1 × 10−3 M)/2-deoxy-d-glucose (2DG; 3 × 10−2 M) to the basolateral culture medium for 60 min or Ringer solution without (control) or with Na2S (2.5 × 10−4 M) for 5 min. Nonparametric Mann-Whitney U-test was employed for statistical analysis. B, top: representative Western blots against total AMPK, phosphorylated (pAMPK), and tubulin (loading control) of H441 monolayers, which were exposed to DNP/2DG, Ringer solution (control, ctrl) or Ringer solution with Na2S (2.5 × 10−4 M). B, bottom: densitometric analysis of blots as shown. Band intensities are given as a ratio of tubulin-normalized pAMPK/AMPK. n = numbers within parentheses. Student's unpaired t-test was employed for statistical analysis (P = 0.8840).