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Titolo:
THE ENERGY-EXPENDITURE OF ACTOMYOSIN-ATPASE, CA2-ATPASE AND NA+,K+-ATPASE IN GUINEA-PIG CARDIAC VENTRICULAR MUSCLE()
Autore:
SCHRAMM M; KLIEBER HG; DAUT J;
Indirizzi:
UNIV MARBURG,INST NORMALE & PATHOL PHYSIOL,DEUTSCH STR 2 D-35033 MARBURG GERMANY TECH UNIV MUNICH,INST PHYSIOL D-80802 MUNICH GERMANY
Titolo Testata:
Journal of physiology
fascicolo: 3, volume: 481, anno: 1994,
pagine: 647 - 662
SICI:
0022-3751(1994)481:3<647:TEOACA>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
SODIUM-CALCIUM EXCHANGE; 2,3-BUTANEDIONE MONOXIME; SARCOPLASMIC-RETICULUM; PAPILLARY-MUSCLE; BASAL-METABOLISM; HUMAN MYOCARDIUM; MYOCYTES; HEART; RAT; ENERGETICS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
47
Recensione:
Indirizzi per estratti:
Citazione:
M. Schramm et al., "THE ENERGY-EXPENDITURE OF ACTOMYOSIN-ATPASE, CA2-ATPASE AND NA+,K+-ATPASE IN GUINEA-PIG CARDIAC VENTRICULAR MUSCLE()", Journal of physiology, 481(3), 1994, pp. 647-662

Abstract

1. The rate of heat production (heat rate) and isometric twitch tension of ventricular trabeculae isolated from guinea-pig heart were measured at 37 degrees C in order to determine the relative contributions of actomyosin-ATPase, Ca2+-ATPase and Na+,K+-ATPase to myocardial energy metabolism. 2. The increase in heat rate recorded during isometric contractions at optimal length (contraction-related heat production) was 19.1 +/- 1.2 mW cm(-3) at a stimulation rate of 2 Hz. The tension-time integral of individual contractions measured under the same conditions was 147 +/- 15 mN s cm(-2). 3. The heat production of the actomyosin-ATPase was determined by inhibiting the contractile proteins with 2,3-butanedione monoxime (BDM). Contraction-related heat production wasreduced by 0.219 +/- 0.010 and the isometric tension-time integral was reduced by 0.288 +/- 0.016 in the presence of 1 mM BDM. From these data an estimate of 0.76 for the relative contribution of the actomyosin-ATPase Do contraction-related heat production was derived. 4. The heat production related to actomyosin-ATPase plus Ca2+-ATPase was studied by blocking Ca2+ influx into the myocardial cells with a solution containing 100 mu M Ca2+ and 400 mu M Ni2+. In this solution contraction-related heat production was reduced by 0.907 +/- 0.012. Comparison ofthis value with the component attributable to the actomyosin-ATPase yields an estimate of 0.15 for the relative contribution of the Ca2+-ATPase to contraction-related heat production. 5. The heat production related to the Na+,K+-ATPase in resting preparations was studied by blocking the sodium pump with 400 mu M dihydro-ouabain (DHO). DHO produceda transient decrease in heat rate lasting 1-2 min, which was followedby a secondary increase. From the heat transient produced by DHO the heat rate related to the Na+,K+-ATPase in the steady state was extrapolated. The relative contribution of the sodium pump to resting heat production was estimated to be 0.17. 6. The heat production related to the Na+,K+-ATPase in contracting preparations was studied by first blocking Ca2+ influx with 100 mu M Ca2+ and 400 mu M Ni2+, and then inhibiting the sodium pump with 400 mu M dihydro-ouabain (DHO). The relativecontribution of the sodium pump to contraction-related heat production extrapolated from these data was 0.10, which agreed well with the fraction of contraction-related heat production persisting after blockage of actomyosin-ATPase and Ca2+-ATPase (0.09). 7. It is concluded thatcontraction-related heat production can be completely accounted for by the three major ATPases, and that under our experimental conditions actomyosin-ATPase, Ca2+-ATPase and Na+,K+-ATPase contribute about 76, 15 and 9%, respectively, to myocardial energy expenditure. 8. In cardiac muscle contracting under aerobic conditions the heat rate measured in the steady state is proportional to the rate of ATP hydrolysis, 1 mu M corresponding to about 11 pmol ATP s(-1). From our heat and tension measurements the mechanical impulse per ATP molecule was calculated to be 0.027 pN s.

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Documento generato il 02/12/20 alle ore 17:05:19