Document Detail

Enhanced cytochrome oxidase activity and modification of lipids in heart mitochondria from hyperthyroid rats.
MedLine Citation:
PMID:  8280784     Owner:  NLM     Status:  MEDLINE    
In order to further investigate the mechanism regulating the control of mitochondrial respiration by thyroid hormones, the effect of the hyperthyroidism on the kinetic characteristics of cytochrome c oxidase in rat heart mitochondria was studied. Mitochondrial preparations from both control and hyperthyroid rats had equivalent Km values for cytochrome c, while the maximal activity of cytochrome oxidase was significantly increased (by around 30%) in mitochondrial preparation from hyperthyroid rats. This enhanced activity of cytochrome oxidase was associated to a parallel increase in mitochondrial State 3 respiration. The hormone treatment resulted in a decrease in the flux control coefficient of the oxidase. The enhanced activity of cytochrome oxidase in hyperthyroid rats does not appear to be dependent on an increase in the mass of this enzyme complex in that the heme aa3 content was equivalent in both hyperthyroid and control preparations. The Arrhenius plot characteristics differ for cytochrome oxidase activity in mitochondria from hyperthyroid rats as compared with control rats in that the breakpoint of the biphasic plot is shifted to a lower temperature. Cardiolipin content was significantly increased in mitochondrial preparations from hyperthyroid rats, while there were no significant alterations in the fatty acid composition of cardiolipin of control and hyperthyroid preparations. The results support the conclusion that the enhanced cytochrome oxidase activity in heart mitochondrial preparations from hyperthyroid rats is due to a specific increase in the content of cardiolipin.
G Paradies; F M Ruggiero; G Petrosillo; E Quagliariello
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1225     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1994 Jan 
Date Detail:
Created Date:  1994-02-15     Completed Date:  1994-02-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  165-70     Citation Subset:  IM    
Department of Biochemistry and Molecular Biology, University of Bari, Italy.
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MeSH Terms
Cardiolipins / chemistry,  metabolism
Electron Transport Complex IV / metabolism*
Fatty Acids / analysis
Hyperthyroidism / metabolism*
Lipid Metabolism*
Mitochondria, Heart / drug effects,  metabolism*
Oxygen Consumption
Rats, Wistar
Thyroid Hormones / pharmacology
Reg. No./Substance:
0/Cardiolipins; 0/Fatty Acids; 0/Thyroid Hormones; EC Transport Complex IV

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