ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary ATP (1–1.2mm) was photoreleased from caged ATP (5mm) in skinned fibres from rat psoas muscle at 15–17° C, to examine the effects of ethylene glycol (EG; 20% in solvent) on the kinetics of isometric contraction. Muscle fibres were stretched by 0.5–2% before photolysis, so that force just before photolysis was almost equal to the steady-state force after photolysis. At the phase of steady-state contraction, force and 500 Hz-stifmess in the presence of EG were 50% and 70% of the controls, respectively, resulting in a higher stiffness-to-force with EG, as reported previously. Following photolysis, force fell before rising to a steady-state plateau. The estimated rate constant of the force decay was approximately 90 s−1, and in the presence of EG was 80–85% of the control. This suggested a small effect of EG on the crossbridge detachment induced by ATP. The rate of force redevelopment was approximately 70 s−1, and EG decreased this rate to 50% of the control. This suggested that EG greatly slows the transition of the crossbridges from the detached state to the reattached force-producing state. The time course of the stiffness signals was consistent with this interpretation. The high stiffness-to-force ratio with EG indicated that EG not only reduces the rate constants which were directly examined in this study but also modifies other aspects of the crossbridge reaction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01874157
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