Table 2.
Effect of MHC composition on parameters of cross-bridge cycling
| n | ktr, s−1 | ATPase, pmol·s−1·mm−3 | Tension Cost, pmol·s−1·mm−1·mN−1 | fapp | gapp | |
|---|---|---|---|---|---|---|
| 100% α-MHC | 12 | 23.9±1.2 | 624.29±23.7 | 15.09±0.75 | 6.84 | 17.06 |
| 60% α-MHC | 10 | 17.9±1.4* | 531.91±44.2 | 13.25±1.15 | NA | NA |
| 0% α-MHC | 10 | 11.4±0.7* | 247.92±13.9* | 7.92±0.95* | 2.47 | 8.93 |
Data are means ± SE; n, number of cardiac preparations. ktr, rate constant of force redevelopment in response to a rapid slack-restretch maneuver; ATPase, rate of ATP hydrolysis; tension cost, ratio of ATPase to isometric force; fapp, derived rate constant of cross-bridge attachment; gapp, derived rate constant of cross-bridge detachment. Derivations of rate constants were performed only in myocardium expressing either 100% or 0% α-MHC. NA, not applicable.
*
Significantly different from hyperthyroid (100% α-MHC) myocardium (P < 0.05).