Fig. 2

Changes in MQAE fluorescence and cell volume in airway ciliary cells in the Cl⁻-free NO₃⁻ solution induced by osmotic stresses. Cells were pretreated with the Cl⁻-free NO₃⁻ solution for 20 min prior to the exposure to osmotic stress. To achieve hypo- or hyper-osmotic stress state, NaNO₃ (30 mM) was removed from or added to the Cl⁻-free NO₃⁻ solution. a–c Hypo-osmotic stress (− 30 mM NaNO₃). Application of hypo-osmotic stress (− 30 mM NaNO₃) did not change the normalized value of MQAE fluorescence intensity (F/F₀) (a), while it significantly decreased the normalized value of the cell volume (V/V₀) (*significant difference at p < 0.05; b). Total MQAE fluorescence intensities were not changed by exposure to hypo-osmotic stress (c). d–f Hyper-osmotic stress (+ 30 mM NaNO₃). Hyper-osmotic stress did not change the normalized MQAE fluorescence (F/F₀) (d), while it significantly increased the normalized value of the cell volume (V/V₀) (*Signficant difference at p < 0.05; e). Total MQAE fluorescence intensities were not changed by the hyper-osmotic stress (f). Symbols in a and d represent the mean; bars and whiskers in b, c, e, f are the mean and standard error of the mean (SEM), respectively