Document Detail

Differential effects of pH on calcium activation of myofilaments of adult and perinatal dog hearts. Evidence for developmental differences in thin filament regulation.
MedLine Citation:
PMID:  2940029     Owner:  NLM     Status:  MEDLINE    
Our results show that calcium activation of myofilament preparations of dog heart in the perinatal period is unaffected by a reduction in pH from 7.0 to 6.5, which, in adult heart myofilaments, induces a 0.4 pCa unit (-log molar free calcium concentration) rightward shift in the relation between pCa and myofibrillar adenosine triphosphatase activity. Acidic pH also had no effect on calcium binding to myofibrillar troponin C of perinatal hearts. The stoichiometry of troponin C bound calcium at full myofilament activation (about 3 mol calcium/mol troponin C) was the same for adult and perinatal heart myofibrils, as was their myofibrillar troponin C content. Moreover, there were no differences in isoelectric pH of troponin C from adult and perinatal hearts. We tested whether variants of myofilament proteins other than troponin C could account for the differential effects of acidic pH. In adult and perinatal dog heart preparations, myosin heavy chain isoenzymes appeared the same as measured, using native pyrophosphate gel electrophoresis. No evidence for thick filament-related calcium regulation in the perinatal heart myofilaments was obtained, when tested in studies in which native thin filaments were displaced with a 10-fold molar excess of pure actin. In preparations in which native thick filaments were displaced with a 10-fold molar excess of pure skeletal muscle myosin, the effects of acidic pH on calcium activation were the same as in native adult and perinatal preparations. Our major conclusion from these results in that the perinatal heart myofilaments are likely to possess variations in thin filament activity and structure.(ABSTRACT TRUNCATED AT 250 WORDS)
R J Solaro; P Kumar; E M Blanchard; A F Martin
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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:  Circulation research     Volume:  58     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1986 May 
Date Detail:
Created Date:  1986-06-30     Completed Date:  1986-06-30     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  721-9     Citation Subset:  IM    
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MeSH Terms
Ca(2+) Mg(2+)-ATPase / metabolism
Calcium / metabolism,  physiology*
Cytoskeleton / metabolism*
Electrophoresis, Polyacrylamide Gel
Heart / growth & development
Hydrogen-Ion Concentration*
Magnesium / metabolism,  physiology
Microfilaments / metabolism*,  physiology
Muscle Proteins / isolation & purification
Myocardium / metabolism*
Grant Support
Reg. No./Substance:
0/Muscle Proteins; 7439-95-4/Magnesium; 7440-70-2/Calcium; EC 3.6.1.-/Ca(2+) Mg(2+)-ATPase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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