Table 1.
Effect of various agents on outward INa-Ca density and Na+–Ca2+ exchanger reversal potential (Erev) in shark ventricular myocytes
| Agent | Iout, pA/pF | 5 mM Ni2+
|
10 μM
KB-R7943
|
INa-Ca (Iout − Iout(Ni)), pA/pF | ΔINa-Ca, inhibition, % | ΔErev, mV | ||
|---|---|---|---|---|---|---|---|---|
| Iout(Ni), pA/pF | Inhibition, % | Iout(KB-R7943), pA/pF | Inhibition, % | |||||
| Control | 8.86 ± 0.76 (12) | 3.84 ± 1.9 (12) | 56.7 ± 2.9 (12) | 3.38 ± 1.6 (4) | 62.5 ± 6.4 (4) | 5.42 ± 0.42 (12) | ||
| Isoproterenol (5 μM) | 6.94 ± 1.47* (3) | 2.88 ± 0.63 (3) | 57.7 ± 3.5 (3) | 4.06 ± 1.2† (3) | 24.0 ± 7.2 (3) | −22.9 ± 1.8 (3) | ||
| Forskolin (10 μM) | 5.65 ± 0.76* (2) | 2.61 ± 0.22 (2) | 54.1 ± 1.5 (2) | 3.04 ± 0.54† (2) | 44.4 ± 0.95 (2) | −29.6 ± 3.7 (2) | ||
Iout was measured in each cell at 50 ms after the onset of depolarization to +60 mV during ramp protocol (Fig. 1D) and was normalized to the cell capacitance to yield current density (pA/pF). ΔINa-Ca represents a difference between INa-Ca in control and INa-Ca in the presence of isoproterenol or forskolin. ΔErev is the amount of change in Erev of the INa-Ca in the presence of isoproterenol or forskolin compared with that in control. Data are represented as the mean ± SEM (number of cells). *, Significantly different from control Iout at P < 0.05;
, significantly different from control INa-Ca at P < 0.05.