2.
[Mg2+]i and pHi values estimated using two methods: (1) from the chemical shifts of β-and γ-ATP or 2) from the chemical shifts of β-ATP and Pi.(See Materials and methods for details). [Mg2+]i and pHi values during [Mg2+]i deple- tion were compared in A and B. In C and D, [Mg2+]i and pHi values were during the elevation of [Mg2+]i. Single (*) and double asterisks (**) indicate P<0.05 and P<0.01 versus control, respectively.
| (A) Exposure to a divalent cation- and Na+-free solution (n = 7). | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1) from β- and γ-ATP | 2) from β-ATP and Pi | ||||||||||||
| [Mg2+]i (mM) | pHi | [Mg2+]i (mM) | pHi | ||||||||||
| Control (0 Ca2+) | 0.70±0.13 | 7.20±0.11 | 0.75±0.09 | 7.09±0.05 | |||||||||
| 0 Ca2+, 0 Mg2+, 0 Na+ (K+) 25–50 min | 0.61±0.07** | 7.09±0.09** | 0.62±0.04** | 7.06±0.04** | |||||||||
| 0 Ca2+, 0 Mg2+, 0 Na+ (K+) 100–125 min | 0.43±0.04** | 7.01±0.08** | 0.46±0.05** | 6.92±0.05** | |||||||||
| (B) Exposure to a divalent cation- and Na+-free solution containing 2-APB (n = 7). | |||||||||||||
| 1) from β- and γ-ATP | 2) from β-ATP and Pi | ||||||||||||
| [Mg2+]i (mM) | pHi | [Mg2+]i (mM) | pHi | ||||||||||
| Control (0 Ca2+) | 0.68±0.04 | 7.21±0.05 | 0.74±0.05 | 7.09±0.04 | |||||||||
| 0 Ca2+, 0 Mg2+, 0 Na+ (K+) +150μM 2-APB 25–50 min | 0.65±0.08* | 7.09±0.08** | 0.68±0.07* | 7.03±0.04** | |||||||||
| 0 Ca2+, 0 Mg2+, 0 Na+ (K+) +150μM 2-APB 100–125 min | 0.60±0.12** | 7.00±0.11** | 0.62±0.08** | 6.94±0.05** | |||||||||
| (C) Exposure to a Ca2+- and Na+-free, high Mg2+ (6.0 mM) solutions (n = 7). | |||||||||||||
| 1) from β- and γ-ATP | 2) from β-ATP and Pi | ||||||||||||
| [Mg2+]i (mM) | pHi | [Mg2+]i (mM) | pHi | ||||||||||
| Control (0 Ca2+) | 0.72±0.10 | 7.20±0.09 | 0.78±0.08 | 7.08±0.12 | |||||||||
| 0 Ca2+, 6.0 Mg2+, 0 Na+ (K+) 25–50 min | 1.11±0.28** | 7.12±0.10** | 1.18±0.28** | 7.03±0.05** | |||||||||
| 0 Ca2+, 6.0 Mg2+, 0 Na+ (K+) 100–125 min | 1.63±0.23** | 6.99±0.11** | 1.79±0.18** | 6.92±0.04** | |||||||||
| (D) Exposure to a Ca2+- and Na+-free, high Mg2+ (6.0 mM) solution containing 2-APB (n = 6). | |||||||||||||
| 1) from β- and γ-ATP | 2) from β-ATP and Pi | ||||||||||||
| [Mg2+]i (mM) | pHi | [Mg2+]i (mM) | pHi | ||||||||||
| Control (0 Ca2+) | 0.70±0.09 | 7.20±0.11 | 0.75±0.04 | 7.10±0.03 | |||||||||
| 0 Ca2+, 6.0 Mg2+, 0 Na+ (K+) +150μM 2-APB 25–50 min | 0.91±0.10** | 7.06±0.07** | 0.93±0.06** | 7.02±0.02** | |||||||||
| 0 Ca2+, 6.0 Mg2+, 0 Na+ (K+) +150μM 2-APB 100–125 min | 1.10±0.08** | 6.99±0.04** | 1.14±0.08** | 6.95±0.03** | |||||||||