| Group . | pCa 6.2 . | pCa 6.1 . | pCa 6.0 . | pCa 5.9 . |
|---|---|---|---|---|
| WT | ||||
| Pre–0.5 µM OM | 4.9 ± 0.7 | 8.7 ± 1.2 | 9.3 ± 1.2 | 12.4 ± 1.9 |
| 0.5 µM OM | 7.7 ± 0.8 (*, P = 0.001) | 10.4 ± 1.4 (*, P = 0.03) | 9.8 ± 1.0 | 11.7 ± 1.3 |
| Pre–1.0 µM OM | 3.7 ± 0.6 | 6.3 ± 0.8 | 7.7 ± 1.2 | 10.2 ± 1.9 |
| 1.0 µM OM | 9.3 ± 0.9 (*, P = 0.001) | 10.2 ± 1.1 (*, P = 0.001) | 9.5 ± 1.2 (*, P = 0.007) | 11.4 ± 1.7 (*, P = 0.03) |
| SA | ||||
| Pre–0.5 µM OM | 4.5 ± 0.9 | 5.3 ± 0.9 | 7.4 ± 1.2 | 9.1 ± 1.2 |
| 0.5 µM OM | 4.9 ± 0.7 | 6.1 ± 1.4 | 7.3 ± 1.0 | 9.1 ± 1.1 |
| Pre–1.0 µM OM | 4.2 ± 0.6 | 5.3 ± 0.7 | 6.9 ± 0.5 | 7.8 ± 0.5 |
| 1.0 µM OM | 6.3 ± 0.7 (*, P = 0.001; &, P = 0.03) | 6.9 ± 0.6 (*, P = 0.008; &, P = 0.04) | 8.1 ± 0.6 (*, P = 0.01) | 8.7 ± 0.4 (*, P = 0.01) |
| Group . | pCa 6.2 . | pCa 6.1 . | pCa 6.0 . | pCa 5.9 . |
|---|---|---|---|---|
| WT | ||||
| Pre–0.5 µM OM | 4.9 ± 0.7 | 8.7 ± 1.2 | 9.3 ± 1.2 | 12.4 ± 1.9 |
| 0.5 µM OM | 7.7 ± 0.8 (*, P = 0.001) | 10.4 ± 1.4 (*, P = 0.03) | 9.8 ± 1.0 | 11.7 ± 1.3 |
| Pre–1.0 µM OM | 3.7 ± 0.6 | 6.3 ± 0.8 | 7.7 ± 1.2 | 10.2 ± 1.9 |
| 1.0 µM OM | 9.3 ± 0.9 (*, P = 0.001) | 10.2 ± 1.1 (*, P = 0.001) | 9.5 ± 1.2 (*, P = 0.007) | 11.4 ± 1.7 (*, P = 0.03) |
| SA | ||||
| Pre–0.5 µM OM | 4.5 ± 0.9 | 5.3 ± 0.9 | 7.4 ± 1.2 | 9.1 ± 1.2 |
| 0.5 µM OM | 4.9 ± 0.7 | 6.1 ± 1.4 | 7.3 ± 1.0 | 9.1 ± 1.1 |
| Pre–1.0 µM OM | 4.2 ± 0.6 | 5.3 ± 0.7 | 6.9 ± 0.5 | 7.8 ± 0.5 |
| 1.0 µM OM | 6.3 ± 0.7 (*, P = 0.001; &, P = 0.03) | 6.9 ± 0.6 (*, P = 0.008; &, P = 0.04) | 8.1 ± 0.6 (*, P = 0.01) | 8.7 ± 0.4 (*, P = 0.01) |
The impact of OM on force generation was measured by incubating WT and SA myocardial preparations with either 0.5 µM or 1.0 µM OM. Baseline forces generated by the myocardial preparations were first measured in Ca2+ solutions with a range of pCa values from 6.2 to 5.9. Forces (in mN/mm2) were subsequently measured on the same preparations using the same range of pCa solutions following a 2-min incubation with either 0.5 µM or 1.0 µM OM. Data from multiple preparations from each heart were averaged, and 12–15 myocardial preparations from four different hearts were used per group. Values are expressed as mean ± SEM. *, Significantly different when comparing the forces generated prior to OM incubation with forces generated following OM incubation within each group. &, Significantly different compared with the corresponding WT group.