Table 4. Maximal tension (Fmax) and Ca2+ sensitivity of force development and the super-relaxed state (SRX) measurements in RLC-depleted/reconstituted skinned porcine cardiac papillary muscle (PM) strips as well as in skinned cardiac PM fibers from transgenic R58Q versus WT mice.
Values are means ± SEM for n = # fibers.
| Parameter | WT | R58Q | S15D-R58Q | |
|---|---|---|---|---|
| Measurements of steady-state force in porcine PM | ||||
| Fmax (in kN/m2) | 41.47 ± 0.65 | 34.08 ± 1.42 ** | 43.88 ± 1.90 ††† | |
| Ca2+-sensitivity, pCa50 | 5.60 ± 0.03 | 5.58 ± 0.01 | 5.64 ± 0.02 | |
| Hill coefficient, nH | 3.35 ± 0.46 | 2.32 ± 0.22 | 2.66 ± 0.15 | |
| n = # fibers | 10 | 10 | 10 | |
| SRX in porcine reconstituted PM | ||||
| P1 | 74.18 ± 2.57 | 60.13 ± 2.65 ** | 70.50 ± 2.90† | |
| T1 (s) | 5.95 ± 0.69 | 6.60 ± 0.75 | 5.51 ± 0.81 | |
| P2 | 25.82 ± 2.57 | 39.87 ± 2.65 ** | 29.51 ± 2.90† | |
| T2 (s) | 56.43 ± 11.88 | 77.69 ± 19.87 | 69.73 ± 13.04 | |
| n = # fibers | 17 | 18 | 16 | |
| SRX in R58Q transgenic mouse PM | ||||
| WT | R58Q | |||
| P1 | 61.89 ± 3.09 | 44.66 ± 4.44 * | ||
| T1 (s) | 5.71 ± 1.35 | 3.89 ± 0.64 | ||
| P2 | 37.81 ± 3.00 | 53.01 ± 4.42 * | ||
| T2 (s) | 269.90 ± 43.96 | 170.80 ± 29.90 | ||
| n= # fibers | 7 | 11 | ||
*
p<0.05,
**
p<0.01 versus WT;
†
p<0.05,
†††
p<0.001 versus R58Q, one-way ANOVA with Tukey’s multiple comparison test (porcine system) and t-test (transgenic mice). P1 and P2 - populations of myosin heads in the fast and slow (respectively) phase of ATP turnover; T1 and T2 - nucleotide turnover times (T, lifetime) in the fast and slow (respectively) phase of ATP turnover.