[Hydration and Dehydration of CO2] [Temperature Dependence] [Title page]

Results and Discussion: Effect of anion transport inhibitors

To demonstrate that the fluorescence time course represents chloride-bicarbonate exchange through the anion exchange protein, band 3, we examined the effect of DIDS and DBDS. These compounds are band 3-specific inhibitors of anion transport. DIDS binds irreversibly and DBDS binds reversibly to band 3; both can inhibit up to 99% of anion exchange. Figure 5 shows that both inhibitors dramatically slow down the fluorescence time course. These results indicate that intracellular SPQ fluorescence monitors chloride-bicarbonate exchange through band 3.

Figure 5. Figure 5.
Figure 5. Effect of anion exchange inhibitors on fluorescence time course. (a) Effect of DIDS, an irreversible inhibitor of anion exchange, on chloride influx resulting from a -65 mM chloride gradient. Equilibrium chloride concentration is 75 mM. Red cells were labeled irreversibly with DIDS before hemolysis as described in Materials and Methods. Exchange time constants were 0.73 ± 0.03 s (control) and 62 ± 4 s (DIDS). (b) Effect of 4 [micro]M DBDS, a reversible inhibitor of anion exchange, on chloride efflux resulting from a +65 mM chloride gradient; equilibrium chloride concentration is 75 mM. Exchange time constants were 0.65 ± 0.04 s (control) and 6.8 ± 0.6 s (DBDS). DBDS exerts a considerable inner filter effect on SPQ fluorescence, artifactually lowering the equilibrium SPQ fluorescence.

[Hydration and Dehydration of CO2] [Temperature Dependence] [Title page]