Influence of Ca2+ on force redevelopment kinetics in skinned rat myocardium.
AUTOR(ES)
Hancock, W O
RESUMO
The influence of Ca2+ on isometric force kinetics was studied in skinned rat ventricular trabeculae by measuring the kinetics of force redevelopment after a transient decrease in force. Two protocols were employed to rapidly detach cycling myosin cross-bridges: a large-amplitude muscle length ramp followed by a restretch back to the original length or a 4% segment length step. During the recovery of force, the length of the central region of the muscle was controlled by using a segment marker technique and software feedback control. Tension redevelopment was fit by a rising exponential governed by the rate constant ktr for the ramp/restretch protocol and kstep for the step protocol. ktr and kstep averaged 7.06 s-1 and 15.7 s-1, respectively, at 15 degrees C; neither ktr nor kstep increased with the level of Ca2+ activation. Similar results were found at submaximum Ca2+ levels when sarcomere length control by laser diffraction was used. The lack of activation dependence of ktr contrasts with results from fast skeletal fibers, in which ktr varies 10-fold from low to high activation levels, and suggests that Ca2+ does not modulate the kinetics of cross-bridge attachment or detachment in mammalian cardiac muscle.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1225261Documentos Relacionados
- Halothane increases Ca2+ efflux via Ca2+ channels of sarcoplasmic reticulum in chemically skinned rat myocardium.
- Calmidazolium alters Ca2+ regulation of tension redevelopment rate in skinned skeletal muscle.
- Isometric force redevelopment of skinned muscle fibers from rabbit activated with and without Ca2+.
- The effects of taurine on Ca2+ uptake by the sarcoplasmic reticulum and Ca2+ sensitivity of chemically skinned rat heart.
- Alterations in contractile properties and Ca2+ transients by beta-and muscarinic receptor stimulation in ferret myocardium.