Inorganic phosphate affects the pCa-force relationship more than the pCa-ATPase by increasing the rate of dissociation of force generating cross-bridges in skinned fibers from both EDL and soleus muscles of the rat

Journal of Muscle Research and Cell Motility
W G Kerrick, Yuanyuan Xu

Abstract

The effect of inorganic phosphate (Pi) on Ca2+ -activation of actomyosin ATPase activity and force in permeabilized (skinned) single extensor digitorum longus (EDL) and soleus muscle fibers of the rat were investigated. Increasing concentrations of Pi decreased force more than ATPase rate at all Ca2+ concentrations and this effect was more pronounced at submaximal Ca2+ -activation. Increasing Pi caused both the normalized pCa-ATPase and pCa-force relationship to be shifted to a higher Ca2+ concentration. At all Ca2+ concentrations ATPase was activated at a lower concentration of Ca2+ than force and this difference in Ca2+ concentration required for the activation of ATPase and force was greater in fast-twitch (EDL) than in slow twitch (soleus) muscle. Soleus muscle pCa-ATPase and pCa-force curves were more sensitive to Ca2+ (pCa50 = 5.97 and 5.89, respectively) than EDL (pCa50 = 5.68 and 5.54, respectively). Finally the shape of the pCa-ATPase and pCa-force curves was similar and not affected by Pi. Analysis shows that Pi increases the rate of dissociation of force generating myosin cross-bridges (ratio of ATPase/force (g(app at all Ca2+ concentration, especially at submaximal Ca2+ -activation levels. Pi effects on g(app) are d...Continue Reading

Citations

Nov 7, 2008·FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology·W Glenn L KerrickDanuta Szczesna-Cordary
Mar 10, 2018·European Journal of Applied Physiology·Ian C SmithWalter Herzog
Nov 26, 2016·Physiological Reports·Ian C SmithA Russell Tupling
Aug 19, 2007·American Journal of Physiology. Heart and Circulatory Physiology·Catalina NormanJonathan P Davis
Sep 18, 2017·Journal of Muscle Research and Cell Motility·Robert Stehle, Chiara Tesi
Oct 1, 2020·Biochemical and Biophysical Research Communications·Ian C SmithWalter Herzog
Apr 14, 2009·Journal of Molecular Biology·Katarzyna KazmierczakDanuta Szczesna-Cordary

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