Table I.
Data from HEK293 Cells Cotransfected with Expression Plasmids Encoding α1, α2δa, and β1a Ca Channel Subunits
| α1 construct | Ca current density | Fast tau ICa | Fast tau IBa | External solution | ||||
|---|---|---|---|---|---|---|---|---|
| pA/pF | ms | ms | ||||||
| α1C | −56 ± 9 (17) | 17 ± 2 (14) | 88 ± 8 (7) | TEAC1 | ||||
| α1C | −17 ± 3 (7) | 38 ± 6 (7) | — | TEAC1 | ||||
| α1C−3′del | −68 ± 21 (7) | 20 ± 4 (8) | 93 ± 21 (6) | TEAC1 | ||||
| CSk1 | −28 ± 5 (12) | 20 ± 1 (11) | 57 ± 11 (6) | TEAC1 | ||||
| CSk2 | −28 ± 11 (8) | 35 ± 4 (9) | 295 ± 38 (8) | TEAC1 | ||||
| CSk2 | −20 ± 7 (5) | 51 ± 8 (5) | 467 ± 107 (4) | NaCl | ||||
| CSk3 | −23 ± 6 (9) | 31 ± 5 (9) | 129 ± 13 (4) | TEAC1 | ||||
| CSk3 | −45 ± 9 (6) | 38 ± 5 (6) | 106 ± 22 (3) | NaCl | ||||
| CSk4 | −16 ± 3 (10) | 70 ± 4 (5) | 75 ± 5 (5) | TEAC1 | ||||
| CSk4 | −13 ± 5 (4) | 82 ± 15 (4) | 80 ± 10 (4) | NaCl | ||||
| CSk5 | −51 ± 12 (8) | 32 ± 4 (10) | 97 ± 9 (8) | TEAC1 | ||||
| CSk5 | −17 ± 6 (5) | 76 ± 7 (5) | 111 ± 6 (7) | NaCl | ||||
| CSk8 | −51 ± 12 (8) | 23 ± 4 (8) | 110 ± 10 (7) | TEAC1 |
The external solution was based upon TEAC1 or NaCl (see materials and methods for compositions). Time constants for inactivation were derived by fitting maximal Ca or Ba currents (i.e., at the peak of the I–V relationship) with one or two exponential functions. Only the fast time constants (fast tau) were analyzed. Currents were evoked by test pulses of 250 or 500 ms, or 1.25 or 5 s, as dictated by the inactivation rate. Mean ± SEM, with the number of cells (n) in parentheses.