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Am J Physiol Heart Circ Physiol 292: H2020-H2022, 2007. First published December 22, 2006; doi:10.1152/ajpheart.00714.2006
0363-6135/07 $8.00
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The rate of tension recovery in cardiac muscle correlates with the relative residual tension prevailing after restretch

Kenneth S. Campbell and Anastasia M. Holbrook

Department of Physiology, University of Kentucky, Lexington, Kentucky

Submitted 5 July 2006 ; accepted in final form 14 December 2006

Isolated cardiac muscles generate tension more quickly at higher levels of Ca2+ activation. We investigated the molecular mechanisms underlying this effect in permeabilized rat myocardial preparations by measuring the rate of tension recovery following brief shortening/restretch perturbations. Separate series of experiments used Ca2+-activating solutions with different pH values (pH 6.75, 7.00, and 7.25) and different phosphate (Pi) concentrations (0, 2.5, and 5.0 mM added Pi) to modulate the recovery kinetics. Subsequent analysis showed that the rate of tension recovery correlated (P < 0.001) with the relative residual tension, that is, the minimum tension measured immediately after restretch normalized to the steady-state isometric tension for the experimental condition. This new finding suggests that the rate at which cardiac muscles develop force increases with the proportion of cross bridges bound to the thin filament and is strong evidence of cooperative contractile activation.

cardiac contractility and energetics; muscle contraction; myocardial contractility


Address for reprint requests and other correspondence: K. S. Campbell, Dept. of Physiology, MS-508, Chandler Medical Center, 800 Rose St., Lexington, KY 40536-0298 (e-mail: k.s.campbell{at}uky.edu)






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