| [3H]Rf Uptake (% of Control) | [14C]Ma Uptake (% of Control) | |
|---|---|---|
| Control | 100.00 ± 5.15 | 100.00 ± 8.48 |
| Choline → Na+ | 91.33 ± 4.33 | 99.66 ± 14.22 |
| K+ → Na+ | 101.73 ± 3.89 | 111.24 ± 21.78 |
| Li+→ Na+ | 101.97 ± 5.79 | 105.65 ± 23.62 |
| 1 mM Ouabain | 93.08 ± 8.61 | 101.74 ± 13.70 |
| Ca2+-free buffer | 100.09 ± 2.45 | 109.89 ± 8.93 |
| 1 mM EGTA | 95.67 ± 5.12 | 91.63 ± 10.06 |
| Control | 100.00 ± 8.73 | 100.00 ± 18.66 |
| l− → Cl− | 78.49 ± 6.181-165 | 91.18 ± 8.21 |
| SCN− → Cl− | 66.85 ± 5.031-165 | 93.32 ± 13.16 |
| Gluconate− → Cl− | 84.39 ± 5.231-160 | 80.54 ± 9.32 |
| [3H]Rf Uptake (% of pH 7) | [14C]Ma Uptake (% of pH 7) | |
|---|---|---|
| pH 3 | 93.94 ± 1.40 | 95.06 ± 11.35 |
| pH 4 | 96.95 ± 4.00 | 88.24 ± 10.82 |
| pH 5 | 97.12 ± 3.72 | 92.49 ± 5.13 |
| pH 6 | 94.26 ± 4.59 | 98.98 ± 12.72 |
| pH 7 | 100.00 ± 3.51 | 100.00 ± 11.85 |
| pH 8 | 96.86 ± 4.93 | 94.90 ± 5.75 |
↵1-160 p < 0.01,
↵1-165 p < 0.001 versus control.
↵1-a Five-day-old BeWo cells were incubated with 5 nM [3H]riboflavin (Rf) and 0.37 μM [14C]mannitol (Ma) for 20 min either in control bathing medium (137 mM NaCl, 5.4 mM KCl, 5.4 mM CaCl2, 1 mM MgSO4, 25 mM glucose, 10 mM HEPES) or in buffers in which NaCl was replaced with 137 mM of various inorganic salts. Ca2+-free buffer contains the same composition of salts as in the control buffer, except 0.1 mM EDTA and no CaCl2 were incorporated. After a 20-min uptake study, cells were washed twice with ice-cold acidic PBS, lysed with 1% Triton X-100, and measured for radioactivity. Each value represents the mean ± S.D. of four experiments.
↵1-b [3H]Riboflavin uptake studies were performed in bathing medium with pH values ranging from 3.0 to 8.0.