Table 2.
Effect of [Mg2+]i on ICa in cardiac myocytes with PP2A and BAY K8644
| Conditions | ICa, pA/pF | %Reduction of ICa | ||
|---|---|---|---|---|
| 0.2 mM [Mg2+]p | 1.8 mM [Mg2+]p | |||
| [Ca2+]o (2.0 mM) | Control | 17.0±2.0 (12) | 5.6±1.0*(10) | 64±2.8 |
| PP2A | 9.8±1.3† (12) | 6.7±0.4*(16) | 25±3.4† | |
| [Ca2+]o (0.5 mM) | Control | 8.0±0.7 (6) | 1.9±0.3*(8) | 75±2.4 |
| BAY K8644 | 16.7±0.9‡ (4) | 3.9±0.6*(4) | 76±2.9 | |
| BAY K8644 + PP2A | 11.6±1.4† (5) | 2.5±0.3*(5) | 75±2.9 | |
Values are means ± SE. The numbers in parentheses indicate replicates for each experimental condition. ICa density in rat ventricular myocytes voltage-clamped with patch electrodes containing the indicated [Mg2+]p. [Ca2+]o (2.0 mM) values were from Ref. 37. Currents were recorded at 5 min after breakthrough into the whole cell patch-clamp configuration. PP2A was included in patch electrode solutions at a concentration of 5 U/ml. BAY K8644 (0.1 μM) was added to superfusion solutions with the indicated [Ca2+]o.
P < 0.05, statistically significant changes of ICa between 0.2 and 1.8 mM [Mg2+]p.
P < 0.05, a reduction of ICa by [Mg2+]i that is significantly different than that produced under control conditions.
P < 0.05, statistically significant difference between control and experimental condition at the same [Mg2+]p.