PMID: 9435629Jan 22, 1998Paper

Mechanism of constant contractile efficiency under cooling inotropy of myocardium: simulation

The American Journal of Physiology
T MikaneH Suga

Abstract

We have reported that, in canine hearts, cardiac cooling to 29 degrees C enhanced left ventricular contractility but changed neither the contractile efficiency of cross-bridge (CB) cycling nor the excitation-contraction coupling energy. The mechanism of this intriguing energetics remained unknown. To get insights into this mechanism, we simulated myocardial cooling mechanoenergetics using basic Ca2+ and CB kinetics. We assumed that both adenosinetriphosphatase (ATPase)-dependent sarcoplasmic reticulum (SR) Ca2+ uptake and CB detachment decelerated with cooling. We also assumed that all the ATPase-independent SR Ca2+ release, Ca2+ binding to and dissociation from troponin, and CB attachment remained unchanged. The simulated cooling shifted the CB force-free Ca2+ concentration curve to a lower Ca2+ concentration, increasing the Ca2+ responsiveness of CB force generation, and increased the maximum Ca(2+)-activated force. The simulation most importantly showed that these cooling effects combined led to a constant contractile efficiency when Ca2+ uptake and CB detachment rate constants changed appropriately. This result seems to account for our experimentally observed constant contractile efficiency under cooling inotropy.

References

Mar 16, 1979·Pflügers Archiv : European journal of physiology·D S Loiselle
Apr 1, 1990·Physiological Reviews·H Suga
Oct 11, 1969·The American Journal of Physiology·L A YeatmanE H Sonnenblick
Sep 1, 1993·Japanese Heart Journal·T NambaH Matsubara
Feb 1, 1996·The Annals of Thoracic Surgery·J C ClevelandA H Harken
Jan 1, 1996·Heart and Vessels·T SakamotoH Suga
Jan 1, 1964·The American Journal of Physiology·R G MONROEJ LEVY

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Citations

Nov 22, 2000·American Journal of Physiology. Heart and Circulatory Physiology·A SaekiH Suga
Jul 11, 2008·American Journal of Physiology. Cell Physiology·Robin H Shutt, Susan E Howlett
Jan 15, 2002·American Journal of Physiology. Heart and Circulatory Physiology·Ju MizunoHiroyuki Suga

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