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Titolo:
MODULATION OF RIGOR AND MYOSIN ATPASE ACTIVITY IN RAT CARDIOMYOCYTES
Autore:
STAPLETON MT; ALLSHIRE AP;
Indirizzi:
UNIV HOSP,UNIV COLL CORK,DEPT PHARMACOL & THERAPEUT CORK IRELAND UNIV HOSP,UNIV COLL CORK,DEPT PHARMACOL & THERAPEUT CORK IRELAND
Titolo Testata:
Journal of Molecular and Cellular Cardiology
fascicolo: 7, volume: 30, anno: 1998,
pagine: 1349 - 1358
SICI:
0022-2828(1998)30:7<1349:MORAMA>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
HEART-CELLS; SKELETAL-MUSCLE; SINGLE CARDIOMYOCYTES; VENTRICULAR MYOCYTES; CONTRACTILE FAILURE; INORGANIC-PHOSPHATE; CREATINE-PHOSPHATE; INFARCT SIZE; MAGNESIUM; ISCHEMIA;
Keywords:
ISCHEMIA; RIGOR; MYOSIN ATPASE; ADP; ACIDOSIS; RAT CARDIOMYOCYTES; FREE ENERGY OF ATP HYDROLYSIS; TROPONIN I;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
M.T. Stapleton e A.P. Allshire, "MODULATION OF RIGOR AND MYOSIN ATPASE ACTIVITY IN RAT CARDIOMYOCYTES", Journal of Molecular and Cellular Cardiology, 30(7), 1998, pp. 1349-1358

Abstract

Ischaemic myocardium undergoes calcium-independent contracture at millimolar tissue ATP, though in actomyosin solutions ATP must be reducedto micromolar before rigor complexes form. This contracture is associated with myosin ATPase activity that may contribute to tissue de-energization. Here we used isolated rat cardiomyocytes permeabilized with digitonin to analyse in parallel how rigor and myosin ATPase activity are modulated by metabolic conditions that develop during ischaemia. At pH 7.1 and 37 degrees C rigor and myosin ATPase showed co-ordinated bell-shaped dependence on ATP concentration over 3-1000 mu M. Rigor, but not myosin ATPase, was inhibited by acidosis (pH 6.2), indicating reduced efficiency of cross-bridge cycling, while both parameters were stimulated by ADP (less than or equal to 1 mM) and unaffected by inorganic phosphate (P-i, 30 mM), AMP, Mg2+, lactate or inhibition of adenylate kinase with diadenosine pentaphosphate. Combined acidosis and high ADP inhibited rigor, while P-i attenuated the enhancement of rigor by ADP. Thus, rigor complex formation activates myosin ATPase in the intact myofilament array, modulated by ADP, P-i and acidosis in the ranges that occur in ischaemia. There was no evidence that adenylate kinase might attenuate falling ATP/ADP ratio at the myofilaments. In combination these effects are sufficient to resolve the apparent discrepancybetween ATP concentrations triggering rigor in actomyosin and onset of contracture in ischaemic myocardium. Since rigor contracture activates myosin ATPase it is likely to exacerbate ATP depletion and thereby limit vital cell functions. This positive feedback is consistent with the abrupt depletion of ATP observed in individual cardiomyocytes undergoing deenergization contracture. (C) 1998 Academic Press.

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Documento generato il 30/11/20 alle ore 16:14:02