Table I.
Apparent Permeability Ratios for Different Anions in CFTR
| Anion | P X/P Cl (inside) | P X/P Cl (outside) | Ion dimensions | |||
|---|---|---|---|---|---|---|
| Å | ||||||
| Thiocyanate | 2.63 ± 0.13 (6) | 2.26 ± 0.19 (4) | 3.60 × 3.60 × 3.60 | |||
| Nitrate | 1.53 ± 0.04 (7) | 1.35 ± 0.03 (4) | 3.10 × 4.76 × 5.17 | |||
| Bromide | 1.23 ± 0.03 (5) | 1.29 ± 0.01 (4) | 3.90 × 3.90 × 3.90 | |||
| Chloride | 1.00 ± 0.01 (10) | 3.62 × 3.62 × 3.62 | ||||
| Iodide | 0.84 ± 0.03 (5) | 0.24 ± 0.03 (5) | 4.32 × 4.32 × 4.32 | |||
| Fluoride | 0.070 ± 0.002 (7) | 0.021 ± 0.003 (5) | 2.72 × 2.72 × 2.72 | |||
| Formate | 0.25 ± 0.01(8) | 0.12 ± 0.01 (4) | 3.40 × 4.62 × 4.82 | |||
| Acetate | 0.090 ± 0.004 (8) | 0.036 ± 0.006 (4) | 3.99 × 5.18 × 5.47 | |||
| Perchlorate | 0.25 ± 0.02 (6) | 0.049 ± 0.006 (5) | 4.63 × 4.64 × 4.91 | |||
| Propanoate | 0.14 ± 0.01 (4) | 0.021 ± 0.002 (4) | 4.12 × 5.23 × 7.05 | |||
| Benzoate | 0.069 ± 0.006 (6) | <0.014 (4) | 3.55 × 6.30 × 8.57 | |||
| Pyruvate | 0.10 ± 0.01 (5) | <0.010 (4) | 4.09 × 5.73 × 6.82 | |||
| Hexafluorophosphate | <0.019 (4) | 4.92 × 4.98 × 5.16 | ||||
| Methane sulfonate | 0.077 ± 0.005 (5) | <0.010 (3) | 5.08 × 5.43 × 5.54 | |||
| Glutamate | 0.096 ± 0.008 (4) | 4.67 × 6.52 × 10.78 | ||||
| Isethionate | 0.13 ± 0.01 (4) | 5.35 × 5.79 × 7.60 | ||||
| Gluconate | 0.071 ± 0.003 (54) | <0.013 (36) | 4.91 × 6.86 × 12.09 | |||
| Glucoheptonate | 0.095 ± 0.005 (4) | 5.50 × 6.51 × 13.54 | ||||
| Glucuronate | 0.13 ± 0.02 (4) | <0.012 (4) | 5.23 × 7.73 × 9.43 | |||
| MES | 0.13 ± 0.01 (4) | 6.00 × 6.99 × 9.65 | ||||
| Galacturonate | 0.079 ± 0.012 (5) | <0.013 (4) | 6.51 × 6.66 × 8.10 | |||
| HEPES (pH 9.0) | 0.092 ± 0.012 (5) | 6.64 × 6.64 × 12.86 | ||||
| TES (pH 9.0) | 0.099 ± 0.012 (4) | 6.63 × 6.75 × 11.35 | ||||
| Lactobionate | 0.048 ± 0.008 (5) | <0.012 (5) | 7.57 × 9.32 × 13.11 | |||
Relative permeabilities (P X/P Cl) of different anions, when present in the intracellular or extracellular solution under biionic conditions, were calculated from macroscopic current reversal potentials (Fig. 1, A and B) as described in methods. Numbers in parentheses indicate the number of patches examined for each ion. Minimum unhydrated ionic dimensions were estimated as described in methods. Maximum permeabilities are given for ions that were not measurably permeant over the voltage range used.