Molecular basis for the influence of muscle length on myocardial performance.
According to Starling's law of the heart, the force of contraction during the ejection of blood is a function of the end-diastolic volume. To seek the molecular explanation of this effect, a study was made of the effects of length on Ca2+ sensitivity during tension development by isolated demembranated cardiac muscle in which the cardiac form of troponin C was substituted with skeletal troponin C. The results of troponin C exchange were compared at sarcomere lengths of 1.9 and 2.4 micrometers. Enhancement of the myocardial performance at the stretched length was greatly suppressed with the skeletal troponin C compared with the cardiac troponin C. Thus the troponin C subunit of the troponin complex that regulates the activation of actin filaments has intrinsic molecular properties that influence the length-induced autoregulation of myocardial performance and may be a basis for Starling's law of the heart.
Babu
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A
Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461.
Sonnenblick
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E
Gulati
J
J
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006224:Cricetinae; D003971:Diastole; D004285:Dogs; D009132:Muscles / Q000032:analysis; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000032:analysis / Q000648:ultrastructure*; D012518:Sarcomeres / Q000502:physiology / Q000648:ultrastructure; D014336:Troponin / Q000502:physiology*; D019209:Troponin C
D014336:Troponin; D019209:Troponin C; D002118:Calcium