Document Detail


Ca(2+)-dependent heat production under basal and near-basal conditions in the mouse soleus muscle.
MedLine Citation:
PMID:  1484367     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
1. The rate of energy expended for the clearance of sarcoplasmic Ca2+ by sarcoreticular Ca2+ uptake process(es), plus the concomitant metabolic reactions, was evaluated from measurements of resting heat production by mouse soleus muscle before and after indirect inhibition of Ca2+ uptake by sarcoplasmic reticulum (SR). 2. Direct inhibition of the Ca2+, Mg(2+)-ATPase of SR membrane in intact muscle preparations exposed to the specific inhibitor 2,5-di(tert-butyl-1,4-benzohydroquinone (tBuBHQ) slowly increased the rate of heat production (E). Indirect inhibition of SR Ca2+ uptake was obtained by reducing sarcoplasmic Ca2+ concentration (Ca2+i) as a consequence of reducing Ca2+ release from the SR using dantrolene sodium. This promptly decreased E by 12%. Exposure of the preparations to an Mg(2+)-enriched environment (high Mg2+) or to the chemical phosphatase 2,3-butanedione monoxime (BDM), two other procedures aimed at decreasing SR Ca2+ release, also acutely decreased E, by 20 and 24%, respectively. 3. Subthreshold-for-contracture depolarization of the sarcolemma achieved by increasing extracellular K+ concentration to 11.8 mM induced a biphasic increase of E: an initial peak to 290% of basal E, followed by a plateau phase at 140% of basal E during which resting muscle tension was increased by less than 3%. Most, if not all, of the plateau-phase metabolic response was quickly suppressed by dantrolene or high Mg2+ or BDM. Another means of increasing SR Ca2+ cycling was to partially remove the calmodulin-dependent control of SR Ca2+ release using the calmodulin inhibitor W-7. The progressive increase in E with 30 microM-W-7 was largely reduced by dantrolene or high Mg2+ or BDM. 4. In the presence of either dantrolene or BDM to prevent the effect of W-7 on SR Ca2+ release, exposure of the muscle to W-7 acutely suppressed about 3% of E. This and the above results confirm that the plasmalemmal, calmodulin-dependent Ca(2+)-ATPase, although a qualitatively essential part of the Ca2+i homeostatic system of the cell, can only be responsible for a very minor part of the energy expenditure devoted to the homeostasis of Ca2+i. Active Ca2+ uptake by SR which, at least in the submicromolar range of Ca2+i, is expected to be responsible for most of this Ca(2+)-dependent energy expenditure, might dissipate up to 25-40% of total metabolic energy in the intact mouse soleus under basal and near-basal conditions.
Authors:
A Chinet; A Decrouy; P C Even
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  455     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1992 Sep 
Date Detail:
Created Date:  1993-02-17     Completed Date:  1993-02-17     Revised Date:  2010-09-07    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  663-78     Citation Subset:  IM    
Affiliation:
Department of Physiology, University of Geneva, Switzerland.
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MeSH Terms
Descriptor/Qualifier:
Animals
Basal Metabolism
Body Temperature Regulation / physiology*
Calcium / metabolism*
Calmodulin / antagonists & inhibitors
Dantrolene / pharmacology
Diacetyl / analogs & derivatives,  pharmacology
Energy Metabolism / physiology*
Ethylmaleimide / pharmacology
Homeostasis
Hydroquinones / pharmacology
Mice
Muscles / metabolism*
Oxygen Consumption / physiology
Sarcoplasmic Reticulum / metabolism
Chemical
Reg. No./Substance:
0/Calmodulin; 0/Hydroquinones; 128-53-0/Ethylmaleimide; 431-03-8/Diacetyl; 57-71-6/diacetylmonoxime; 7261-97-4/Dantrolene; 7440-70-2/Calcium; 88-58-4/2,5-di-tert-butylhydroquinone
Comments/Corrections

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