Tension Recovery in Permeabilized Rat Soleus Muscle Fibers after Rapid Shortening and Restretch

摘要: Permeabilized rat soleus muscle fibers were subjected to rapid shortening/restretch protocols (20% length, 20 ms duration) in solutions with pCa values ranging from 6.5 4.5. Force redeveloped after each restretch but temporarily exceeded the steady-state isometric tension reaching a maximum value ∼2.5 s relengthening. The relative size of overshoot was <5% and 4.5 equaled 17% ± 4% at 6.0 (approximately half-maximal Ca2+ activation). Muscle stiffness estimated during activations by imposing length steps different time intervals repeated perturbations. Relative correlated (p < 0.001) recovery, suggesting that overshoots reflect temporary increase number attached cross-bridges. Rates recovery (ktr) residual force prevailing immediately restretch. also recovered more quickly 5.7 ≤ 5.9 than (ANOVA, p 0.05). These results show ktr measurements underestimate rate development submaximal suggest is limited primarily availability actin binding sites.