TABLE 2.
Summary of the initial rate of decrease in [Mg2+]i at 25°C
| Experimental conditions | Initial [Mg2+]i | Initial Δ[Mg2+]i/Δt | n |
|---|---|---|---|
| (mM) | (μM/s) | ||
| 140 mM [Na+]o | |||
| Chelator loading/[Ca2+]o* | |||
| –/0 mM | 1.50 ± 0.060 | −1.16 ± 0.049 | 8 |
| BAPTA/0 mM | 1.46 ± 0.054 | −1.32 ± 0.109 | 7 |
| Dimethyl BAPTA/0 mM | 1.49 ± 0.072 | −1.26 ± 0.146 | 4 |
| –/0.5 mM | 1.48 ± 0.065 | −1.09 ± 0.106 | 5 |
| –/1.0 mM | 1.47 ± 0.050 | −1.24 ± 0.098 | 5 |
| –/2.0 mM | 1.47 ± 0.063 | −0.75 ± 0.123 | 5 |
| BAPTA/2.0 mM | 1.53 ± 0.047 | −1.27 ± 0.115 | 6 |
| 70 mM [Na+]o | |||
| [K+]p/[K+]o† | |||
| 135 mM/75 mM | 1.57 ± 0.094 | −0.98 ± 0.057 | 8 |
| 135 mM/0 mM | 1.57 ± 0.053 | −0.85 ± 0.068 | 11 |
| 0 mM/0 mM | 1.54 ± 0.081 | −0.99 ± 0.117 | 7 |
| [K+]p-[Cl−]p/[K+]o-[Cl−]o‡ | |||
| 0 mM-0 mM/0 mM-0 mM | 1.78 ± 0.048 | −1.03 ± 0.075 | 5 |
Columns contain mean ± SE values of initial [Mg2+]i (second column) and initial Δ[Mg2+]i/Δt (third column) from n cells (rightmost column) in each experimental condition (leftmost column). For the statistics, we included data only from the cells that were moderately loaded with Mg2+ (i.e., initial [Mg2+]i between 1.2 mM and 2.0 mM).
Initial Δ[Mg2+]i/Δt values at 140 mM [Na+]o and 5.6 mM [K+]o (cf. Figs. 4 and 5) measured with or without intracellular loading of the Ca2+ chelator at indicated [Ca2+]o.
Cells were patch-clamped at the holding potential of −13 mV. Initial Δ[Mg2+]i/Δt values were estimated at 70 mM [Na+]o without intracellular chelator loading and in the essential absence of extracellular Ca2+ (cf. Fig. 6). [K+]p/[K+]o, combination of K+ concentration in the pipette solution ([K+]p) and in the extracellular solution. 135 mM/75 mM, 135 K-10 Na pipette solution and 75 K-70 Na extracellular solution. 135 mM/0 mM, 135 K-10 Na pipette solution and 0 K-70 Na extracellular solution. 0 mM/0 mM, 145 Cs pipette solution and 0 K-70 Na extracellular solution.
Experimental conditions were identical to those described in previous footnote, except that the extracellular solution (0 K-70 Na-0 Cl) and the pipette solution (145 Cs-0 Cl solution) did not contain Cl−. [Cl−]p and [Cl−]o, Cl− concentrations in the pipette solution and in the extracellular solution, respectively.