Figure 5.

Effects of decreased intracellular Cl⁻ ([Cl⁻]_i) on ciliary beat frequency (CBF) and ciliary beat distance (CBD). (A) Effects of Cl⁻-free (NO₃⁻) solution on CBF, CBD and fluorescence ratio (F₀/F) of N-ethoxycarbonylmethyl-6-methoxyquinolinium bromide (MQAE). First, the perfusion solution was switched from a CO₂/HCO₃⁻-containing solution to a CO₂/HCO₃⁻-free solution. This switch decreased F₀/F (decrease in [Cl⁻]_i) due to Na⁺-HCO₃⁻ cotransporter and Cl⁻/HCO₃⁻ exchange inhibition. The decreasing extracellular Cl⁻ concentration ([Cl⁻]_o) decreased [Cl⁻]_i. The decreased levels of F₀/F were dependent on [Cl⁻]_o. The decreases in [Cl⁻]_i increased CBD, the levels of which are dependent on [Cl⁻]_i. However, a decreased [Cl⁻]_i did not increase CBF. (B) Effects of bumetanide (bum), daidzein and carbocisteine (CCis) on CBF, CBD and F₀/F ([Cl-]_i). Experiments were performed in a CO₂/HCO₃⁻-free solution. Bum, daidzein and CCis decreased F₀/F, indicating decreases in [Cl⁻]_i. These decreases in [Cl⁻]_i increased CBD, but CBF remained unchanged. (C) Effects of Cl⁻ channel blockers on CBF, CBD and F₀/F ([Cl⁻]_i). 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and a cystic fibrosis transmembrane conductance regulator inhibitor (CFTR(inh)-172) increased F₀/F ([Cl⁻]_i). Increases in [Cl⁻]_i (F₀/F) decreased both CBF and CBD. (D) Effects of Cl⁻-free (NO₃⁻) solution, bum, daidzein and CCis on CBF and CBD at 25 °C. Unlike at 37 °C, Cl⁻-free (NO₃⁻) solution, bum, daidzein and CCis increased both CBF and CBD. Thus, a decrease in [Cl⁻]_i enhances both CBF and CBD at 25 °C. * indicates results significantly different from the control values (p < 0.05). Error bars indicate SE.