Bound calcium and force development in skinned cardiac muscle bundles: Effect of sarcomere length

Polly Hofmann, Franklin Fuchs

Research output: Contribution to journalArticle

59 Citations (Scopus)

Abstract

There is evidence that the steep acending limb of the force-length curve in cardiac muscle (Frank-Starling relation) is based on a length-dependence of myofilament Ca2+ sensitivity. Previous work from this laboratory has indicated that in the sarcomere length range corresponding to the ascending limb of the cardiac force length curve (1.7 to 2.3 μm) the Ca2+-troponin C affinity is length-dependent. In this study Ca2+ binding to chemically skinned bovine cardiac muscle bundles was measured during ATP-induced force generation with fiber bundles having sarcomere lengths of 2.2 to 2.4 μm and 1.6 to 1.8 μm. A double isotope technique was used to make concurrent determinations of the force-pCa and bound Ca2+-pCa relationships. At the longer sarcomere lengths the fibers bound, at saturation, an amount of Ca2+ equivalent to ∼3 mol Ca2+/mol troponin C. Force development appeared to be coupled to titration of the single, low-affinity Ca2+-specific site. In the pCa range 7.0 to 6.0 sarcomere length had no effect on Ca2+ binding. In the pCa range 6.0 to 5.0, in which force increased steeply, there was, in addition to a decreased relative force, a significant reduction in bound Ca2+ at the shorter sarcomere length. Thus sarcomere length appears to influence the Ca2+ binding properties of the regulatory site on troponin C. These data provide direct evidence that length-dependent modulation of Ca2+-troponin C affinity may make a major contribution to the force-length relationship in cardiac muscle.

Original languageEnglish (US)
Pages (from-to)667-677
Number of pages11
JournalJournal of Molecular and Cellular Cardiology
Volume20
Issue number8
DOIs
StatePublished - Jan 1 1988

Fingerprint

Sarcomeres
Troponin C
Myocardium
Calcium
Extremities
Starlings
Myofibrils
Isotopes
Adenosine Triphosphate

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

Cite this

Bound calcium and force development in skinned cardiac muscle bundles : Effect of sarcomere length. / Hofmann, Polly; Fuchs, Franklin.

In: Journal of Molecular and Cellular Cardiology, Vol. 20, No. 8, 01.01.1988, p. 667-677.

Research output: Contribution to journalArticle

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