Document Detail

Molecular basis of depression of Ca2+ sensitivity of tension by acid pH in cardiac muscles of the mouse and the rat.
MedLine Citation:
PMID:  8989647     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Acid pH decreases the Ca2+ sensitivity of myocardial tension generation, and recent studies have suggested that regulatory proteins are involved. The current study defines the molecular basis of this effect on troponin C (TnC) and troponin I (TnI) and also addresses previous differences between the rat and mouse. METHODS AND RESULTS: Endogenous cardiac TnC and cardiac TnI in isolated trabeculae from mice and rats were exchanged with their fast-twitch skeletal muscle counterparts. A cardiac-skeletal TnC chimera was used to define the target region for proton action on cardiac TnC. Finally, cardiac TnC and skeletal TnC were genetically modified by insertion of a tryptophan for phenylalanine-26 to probe the pH effects with fluorescence spectroscopy. The pH 6.2 effects on Ca2+ sensitivity of force development in mouse and rat cardiotrabeculae are largely accounted for by the proton influences on TnC (23%) and TnI (53%). In cardiac TnC, residues 1 to 41 provide the target region. Comparison of the Ca(2+)-induced fluorescence in isolated cardiac TnC and skeletal TnC also indicated a greater pH effect in the cardiac isoform. CONCLUSIONS: The studies provide firm evidence that both TnC and TnI moieties are involved in the mechanism of acidosis causing reduction in the Ca sensitivity of force development in the myocardium. The findings rule out the possibility of interspecies variations in the underlying mechanisms. The genetically designed TnCs and a chimera demonstrate that the observed TnC-mediated difference in the pH effects on Ca2+ sensitivity of tension between cardiac and skeletal muscles is preserved in these isolated proteins. The N-terminal amino acid residues 1 to 41 in cardiac TnC are established as the pH sensor of this protein in the mouse as in the rat.
X L Ding; A B Akella; E H Sonnenblick; V G Rao; J Gulati
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of cardiac failure     Volume:  2     ISSN:  1071-9164     ISO Abbreviation:  J. Card. Fail.     Publication Date:  1996 Dec 
Date Detail:
Created Date:  1997-03-25     Completed Date:  1997-03-25     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9442138     Medline TA:  J Card Fail     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  319-26     Citation Subset:  IM    
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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MeSH Terms
Calcium / metabolism*
Culture Techniques
Hydrogen-Ion Concentration*
Molecular Biology
Myocardial Contraction* / physiology
Reference Values
Sensitivity and Specificity
Troponin / administration & dosage,  pharmacology*
Grant Support
Reg. No./Substance:
0/Troponin; 7440-70-2/Calcium

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