ATP splitting by half the cross-bridges can explain the twitch energetics of mouse papillary muscle

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Title ATP splitting by half the cross-bridges can explain the twitch energetics of mouse papillary muscle
Author Widen, Cecilia; Barclay, Christopher John
Journal Name The Journal of Physiology
Year Published 2006
Place of publication Oxford, UK
Publisher Blackwell Publishing Ltd
Abstract The aim of this study was to quantify the fraction of cross-bridges that cycle during a cardiac twitch. Measurements of the energetics of contracting left ventricular mouse papillary muscle were made in vitro (27C) using the myothermic technique. Enthalpy output was partitioned into force-dependent and force-independent components using 2,3-butanedione monoxime (BDM) to selectively inhibit cross-bridge cycling. For isometric contractions and a contraction frequency of 2 Hz the net enthalpy output was 5.7 ±0.8 mJ/g/twitch and initial enthalpy output was 2.3 ±0.3 mJ/g/twitch (n =11). Assuming that low concentrations of BDM did not affect Ca2+ cycling, force-independent enthalpy output was 18.6 ±1.9% (n =7) of the initial enthalpy output. Enthalpy output decreased with increased contraction frequency but was independent of shortening velocity. On the basis of these values, it was calculated that the twitch energetics were consistent with ATP splitting by half the cross-bridges and the pumping of one Ca2+ into the sarcoplasmic reticulum for every three cross-bridge cycles. The simplest interpretation is that half the cross-bridges completed one ATP-splitting cycle in each twitch. The lack of influence of shortening velocity on energy cost supports the idea that the amount of energy to be used is determined early in a twitch and is not greatly influenced by events that occur during the contraction.
Peer Reviewed Yes
Published Yes
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Volume 573
Issue Number 1
Page from 5
Page to 15
ISSN 0022-3751
Date Accessioned 2006-07-10
Language en_AU
Research Centre Menzies Health Institute Qld
Faculty Griffith Health Faculty
Subject Animal Physiology-Cell
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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