The elementary force generation process probed by temperature and length perturbations in muscle fibres from the rabbit

Abstract

Single chemically permeabilized fibres from rabbit psoas muscle were activated maximally at 5–6 °C and then exposed to a rapid temperature increase (‘T‐jump’) up to 37 °C by passing a high‐voltage pulse (40 kHz AC, 0.15 ms duration) through the fibre length. Fibre cooling after the T‐jump was compensated by applying a warming (40 kHz AC, 200 ms) pulse. Tension and changes in sarcomere length induced by the T‐jumps and by fast length step perturbations of the fibres were monitored. In some experiments sarcomere length feedback control was used. After T‐jumps tension increased from ∼55 kN m−2 at 5–6 °C to ∼270 kN m−2 at 36–37 °C, while stiffness rose by ∼15 %, suggesting that at a higher temperature the myosin head generates more force. The temperature‐tension relation became less steep at temperatures above 25°C, but was not saturated even at near‐physiological temperature. Comparison of tension transients induced by the T‐jump and length steps showed that they are different. The T‐jump transients were several times slower than fast partial tension recovery following length steps at low and high temperature (phase 2). The kinetics of the tension rise after the T‐jumps was independent of the preceding length changes. When the length steps were applied during the tension rise induced by the T‐jump, the observed complex tension transient was simply the sum of two separate responses to the mechanical and temperature perturbations. This demonstrates the absence of interaction between these processes. The data suggest that tension transients induced by the T‐jumps and length steps are caused by different processes in myosin cross‐bridges.

Why Muscle is an Efficient Shock Absorber

“…Background was subtracted as described [11], [14]. The positions of some X-ray reflections of interest are marked.…”

Temperature change as a probe of muscle crossbridge kinetics: a review and discussion

“…This confirms that the transition is endothermic, but the DH value is much less than that for the A1-A2 transition described above, 114 zJ per attached head, obtained from the temperature dependence of isometric force. Redrawn from Bershitsky & Tsaturyan (2002). (b) Heat change during the rapid tension recovery after a quick release.…”

“…Their analysis, based on fitting the responses with multiple exponential components, concludes that a component within the length-step response represents the same process as a component in the temperature-step response. This conclusion is challenged by Bershitsky & Tsaturyan (2002) who showed that there is no interaction between the two types of perturbation response when they are applied together, and conclude that the two types of response represent different processes. We propose a new explanation of the different time courses of the force response to length step and to temperature jump ( §6, below).…”

Very low force-generating ability and unusually high temperature-dependency in hummingbird flight muscle fibers

“…Human vastus lateralis fibers had a Q 10-force of force generation of ~2.2 from 12 to 22°C in one study (Bottinelli et al, 1996). An approximate fivefold increase in force generated in rabbit psoas fibers, following a rapidly induced temperature jump of more than 30°C (from ~5 tõ 36°C), has been reported (Bershitsky and Tsaturyan, 2002). Q 10-force values for force generation in frog fibers are even lower [~1.2-1.4 (reviewed in Rall and Woledge, 1990;Tsaturyan et al, 1999)].…”