| Group . | krel (s−1) . | kdf (s−1) . | P1 . | P2 . | P3 . | Pdf . |
|---|---|---|---|---|---|---|
| WT | ||||||
| Pre-OM | 345.39 ± 16.71 | 4.21 ± 0.30 | 0.554 ± 0.02 | −0.093 ± 0.01 | 0.165 ± 0.01 | 0.258 ± 0.01 |
| 0.5 µM OM | 171.24 ± 14.54 (*, P < 0.0001) | 3.56 ± 0.19 | 0.665 ± 0.01 (*, P = 0.03) | 0.012 ± 0.01 (*, P = 0.02) | 0.158 ± 0.01 | 0.146 ± 0.02 (*, P = 0.001) |
| 1.0 µM OM | 89.95 ± 14.26 (*, P < 0.0001) | 3.18 ± 0.37 (*, P = 0.04) | 0.792 ± 0.03 (*, P < 0.0001) | 0.076 ± 0.01 (*, P < 0.0001) | 0.155 ± 0.02 | 0.079 ± 0.01 (*, P < 0.0001) |
| SA | ||||||
| Pre-OM | 217.15 ± 23.47 (&, P = 0.001) | 4.23 ± 0.09 | 0.561 ± 0.02 | 0.046 ± 0.02 (&, P = 0.001) | 0.179 ± 0.01 | 0.133 ± 0.01 (&, P = 0.0005) |
| 0.5 µM OM | 157.48 ± 29.34 | 2.99 ± 0.15 (*, P = 0.02) | 0.665 ± 0.02 (*, P = 0.04) | 0.110 ± 0.04 (&, P = 0.03) | 0.223 ± 0.02 (&, P = 0.04) | 0.113 ± 0.03 |
| 1.0 µM OM | 61.67 ± 8.28 (*, P = 0.0002) | 2.30 ± 0.18 (*, P = 0.0002) | 0.653 ± 0.02 (&, P = 0.002) | 0.118 ± 0.01 | 0.161 ± 0.01 | 0.043 ± 0.01 (*, P = 0.01) |
| Group . | krel (s−1) . | kdf (s−1) . | P1 . | P2 . | P3 . | Pdf . |
|---|---|---|---|---|---|---|
| WT | ||||||
| Pre-OM | 345.39 ± 16.71 | 4.21 ± 0.30 | 0.554 ± 0.02 | −0.093 ± 0.01 | 0.165 ± 0.01 | 0.258 ± 0.01 |
| 0.5 µM OM | 171.24 ± 14.54 (*, P < 0.0001) | 3.56 ± 0.19 | 0.665 ± 0.01 (*, P = 0.03) | 0.012 ± 0.01 (*, P = 0.02) | 0.158 ± 0.01 | 0.146 ± 0.02 (*, P = 0.001) |
| 1.0 µM OM | 89.95 ± 14.26 (*, P < 0.0001) | 3.18 ± 0.37 (*, P = 0.04) | 0.792 ± 0.03 (*, P < 0.0001) | 0.076 ± 0.01 (*, P < 0.0001) | 0.155 ± 0.02 | 0.079 ± 0.01 (*, P < 0.0001) |
| SA | ||||||
| Pre-OM | 217.15 ± 23.47 (&, P = 0.001) | 4.23 ± 0.09 | 0.561 ± 0.02 | 0.046 ± 0.02 (&, P = 0.001) | 0.179 ± 0.01 | 0.133 ± 0.01 (&, P = 0.0005) |
| 0.5 µM OM | 157.48 ± 29.34 | 2.99 ± 0.15 (*, P = 0.02) | 0.665 ± 0.02 (*, P = 0.04) | 0.110 ± 0.04 (&, P = 0.03) | 0.223 ± 0.02 (&, P = 0.04) | 0.113 ± 0.03 |
| 1.0 µM OM | 61.67 ± 8.28 (*, P = 0.0002) | 2.30 ± 0.18 (*, P = 0.0002) | 0.653 ± 0.02 (&, P = 0.002) | 0.118 ± 0.01 | 0.161 ± 0.01 | 0.043 ± 0.01 (*, P = 0.01) |
Stretch activation amplitudes were normalized to prestretch steady-state Ca2+-activated force, which refers to the activation level (pCa 6.1; ∼30% of maximal Ca2+-activated force) as described in Materials and methods. Data from multiple preparations from each heart were averaged, and 12–15 myocardial preparations from four or five different hearts were used per group. Values are expressed as mean ± SEM. kdf, rate of XB recruitment; krel, rate of XB detachment; P1, XB stiffness; P2, magnitude of XB detachment; P3, new steady-state force reached following a quick 2% stretch in ML; Pdf, magnitude of XB recruitment. *, Significantly different compared with the corresponding pre-OM group. &, Significantly different compared with the corresponding WT group.