Molecular basis for the influence of muscle length on myocardial performance

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Science  01 Apr 1988:
Vol. 240, Issue 4848, pp. 74-76
DOI: 10.1126/science.3353709


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.