Comparison of cross-bridge cycling kinetics in neonatal vs. adult rat ventricular muscle

Y. S. Prakash, Mark J. Cody, Philippe R. Housmans, James D. Hannon, Gary C. Sieck

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The developmental shift in contractile protein isoform expression in the rodent heart likely affects actin-myosin cross-bridge interactions. We compared the Ca2+ sensitivity for force generation and cross-bridge cycling kinetics in neonatal (postnatal days 0-3) and adult (day 84) rats. The force-pCa relationship was determined in Triton-X skinned muscle bundles activated at pCa 9.0 to 4.0. In strips maximally activated at pCa 4.0, the following parameters of cross-bridge cycling were measured: (1) rate of force redevelopment following rapid shortening and restretching (k(tr)); and (2) isometric stiffness at maximal activation and in rigor. The fraction of attached cross-bridges (α(fs)) and apparent rate constants for cross-bridge attachment (f(app)) and detachment (g(app)) were derived assuming a two-state model for cross-bridge cycling. Compared to the adult, the force-pCa curve for neonatal cardiac muscle was significantly shifted to the left. Neonatal cardiac muscle also displayed significantly smaller α(fs), slower k(tr) and f(app); however, g(app) was not significantly different between age groups. These data indicate that weaker force production in neonatal cardiac muscle involves, at least in part, less efficient cross-bridge cycling kinetics.

Original languageEnglish (US)
Pages (from-to)717-723
Number of pages7
JournalJournal of Muscle Research and Cell Motility
Issue number7
StatePublished - 1999

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Cell Biology


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