Autori: Stehle R., Solzin J., Iorga B., Poggesi C.

Editorial: Springer-Verlag, Pflugers Arch - Eur J Physiol, DOI 10.1007/s00424-008-0630-2, 2009.

Rezumat:

Muscle contraction results from force-generating interactions between myosin cross-bridges on the thick filament and actin on the thin filament. The force-generating interactions are regulated by Ca2+ via specialized proteins of the thin filament. It is controversial how the contractile and regulatory systems dynamically interact to determine the time course of muscle contraction and relaxation. Whereas kinetics of Ca2+-induced thin filament regulation is often investigated with isolated proteins, force kinetics is usually studied in muscle fibres. The gap between studies on isolated proteins and structured fibres is now bridged by recent techniques that analyse the chemical and mechanical kinetics of small components of a muscle fibre, subcellular myofibrils isolated from skeletal and cardiac muscle. Formed of serially arranged repeating units called sarcomeres, myofibrils have a complete, fully structured, ensemble of contractile and Ca2+-regulatory proteins. The small diameter of myofibrils (few µm) facilitates analysis of the kinetics of sarcomere contraction and relaxation induced by rapid changes of [ATP] or [Ca2+]. Among the processes studied on myofibrils are: i.) the Ca2+-regulated switch-on/off of the troponin-complex; ii.) the chemical steps in the cross-bridge ATPase cycle, iii.) the mechanics of force-generation, and iv.) the length-dynamics of individual sarcomeres. These studies give new insights into the kinetics of thin filament regulation and of cross-bridge turnover, how cross-bridges transform chemical energy into mechanical work, and suggest that the cross-bridge ensembles of each half-sarcomere cooperate with each other across the half-sarcomere borders. Additionally, we now have a better understanding of muscle relaxation and its impairment in certain muscle diseases.

Cuvinte cheie: muscle contraction, muscle relaxation, myocardial contraction, myocardial relaxation, myofibrils, sarcomeres, calcium, thin-filament regulation, cross-bridge kinetics // muscle contraction, muscle relaxation, myocardial contraction, myocardial relaxation, myofibrils, sarcomeres, calcium, thin-filament regulation, cross-bridge kinetics

URL: http://www.ncbi.nlm.nih.gov/pubmed/19165498?ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum