Table 3.
Effect of 2.5 μM thapsigargin on spontaneous [Ca2+]i transients and action potentials (APs) in rabbit atrioventricular node cells.
| Parameters | Control | At 5 s after thapsigargin exposure | At 15 sec after thapsigargin exposure | At 30 s after thapsigargin exposure |
|---|---|---|---|---|
| Spontaneous AP (n = 10) | ||||
| Rate (beats/s) | 3.22 ± 0.25 | 3.40 ± 0.33 | 2.44 ± 0.36* | 1.48 ± 0.44** |
| [% change, compared with control] | [5.6 ± 4.3%] | [−25.1 ± 6.9%] | [−57.8 ± 10.9%] | |
| Slope of pacemaker diastolic depolarization (mV s−1) | 97.7 ± 18.9 | 102.0 ± 17.6 | 68.1 ± 18.5* | 33.6 ± 10.3** |
| [% change] | [12.6 ± 12.1%] | [−31.9 ± 7.4%] | [−65.1 ± 11.7%] | |
| Maximal diastolic potential (MDP, mV) | −52.74 ± 3.09 | −50.55 ± 3.02 | −50.68 ± 2.71 | −46.31 ± 2.47* |
| [% change] | [−4.1 ± 1.4%] | [−3.6 ± 1.6%] | [−11.5 ± 3.5%] | |
| AP amplitude (mV) | 63.96 ± 3.99 | 59.65 ± 3.75 | 59.68 ± 4.46 | 43.20 ± 9.82* |
| [% change] | [−6.5 ± 1.9%] | [−7.2 ± 3.7%] | [−35.0 ± 14.4%] | |
| Spontaneous [Ca2+]itransient (n = 7) | ||||
| Rate (beats/s) | 3.27 ± 0.41 | 4.36 ± 0.36* | 1.95 ± 0.56* | 0.35 ± 0.34** |
| [% change, compared with control] | [38.7 ± 13.1%] | [−43.9 ± 13.1%] | [−87.5 ± 12.5%] | |
| Percentage increase of diastolic Ca2+ baseline compared with control (%) | – | 4.52 ± 2.49% | −7.05 ± 4.89 | −27.47 ± 7.21$$ |
When the data were analysed for this table, if spontaneous activity had stopped in the presence of thapsigargin, the values for maximal diastolic potential were taken as the ‘resting’ potential, and the values for AP rate and other AP parameters were taken as 0; and spontaneous [Ca2+]i transient rate was taken as 0.
*
P < 0.05, versus control.
**
P < 0.01 versus control.
$$
P < 0.01 compared with 0.