Table 1.
Comparison of experimental data on GLT-1 reversal potential with theoretical predictions for different stoichiometries
| Theory | ||||||
|---|---|---|---|---|---|---|
| Experiments | 3Na+, H+, glu−/K+ | 2Na+, H+, glu−/K+ | 3Na+, 2H+, glu−/K+ | 5Na+, H+, 2glu−/K+ | ||
| ControlErev | −12.2 ± 1.6 (n = 22) | −11.9 (p = 0.85) | −54.1 (p = 9 × 10−18) | −15.8 (p = 3 × 10−2) | −27.1 (p = 3.9 × 10−9) | |
| ΔErev(Δ[Na]o) | −27.8 ± 2.5 (n = 7) | −26.3 (p = 0.56) | −35.1 (p = 2.6 × 10−2) | −17.5 (p = 5.9 × 10−3) | −29.2 (p = 0.59) | |
| ΔErev(Δ[H]o) | −19.3 ± 3.2 (n = 6) | −17.7 (p = 0.66) | −35.5 (p = 3.9 × 10−3) | −23.6 (p = 0.23) | −11.8 (p = 6.8 × 10−2) | |
| ΔErev(Δ[K]o) | +14.6 ± 2.6 (n = 11) | +18.6 (p = 0.16) | +37.1 (p = 6.4 × 10−6) | +12.4 (p = 0.41) | +12.4 (p = 0.41) | |
| ΔErev(Δ[glu]o) | +15.1 ± 1.6 (n = 7) | +14.1 (p = 0.57) | +28.2 (p = 2.1 × 10−4) | +9.4 (p = 1.3 × 10−2) | +18.8 (p = 6.5 × 10−2) | |
All reversal potentials are in millivolts. Data on the left give the mean reversal potential in control solution (±SEM; number of cells in brackets) and the reversal potential shifts seen on lowering [Na+]o from 101 to 51 mm, changing external pH from 7.4 to 8.0, lowering external [K+]o from 42.5 to 10 mm, and raising external [glu−] from 100 to 300 μm. Columns on the right show the predicted reversal potentials for four different transporter stoichiometries (described as cotransported substrates/countertransported substrate). In brackets after each value is shown the p value from a two-tailedt test comparing the theoretical prediction with the experimental data.