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Type: Artigo de periódico
Title: Enhanced Calcium Mobilization In Rat Ventricular Myocytes During The Onset Of Pressure Overload-induced Hypertrophy.
Author: Carvalho, Beatriz M R
Bassani, Rosana A
Franchini, Kleber G
Bassani, José W M
Abstract: Early cardiovascular changes evoked by pressure overload (PO) may reveal adaptive strategies that allow immediate survival to the increased hemodynamic load. In this study, systolic and diastolic Ca(2+) cycling was analyzed in left ventricular rat myocytes before (day 2, PO-2d group) and after (day 7, PO-7d group) development of hypertrophy subsequent to aortic constriction, as well as in myocytes from time-matched sham-operated rats (sham group). Ca(2+) transient amplitude was significantly augmented in the PO-2d group. In the PO-7d group, intracellular Ca(2+) concentration ([Ca(2+)](i)) was reduced during diastole, and mechanical twitch relaxation (but not [Ca(2+)](i) decline) was slowed. In PO groups, fractional sarcoplasmic reticulum (SR) Ca(2+) release at a twitch, SR Ca(2+) content, SR Ca(2+) loss during diastole, and SR-dependent integrated Ca(2+) flux during twitch relaxation were significantly greater than in sham-operated groups, whereas the relaxation-associated Ca(2+) flux carried by the Na(+)/Ca(2+) exchanger was not significantly changed. In the PO-7d group, mRNA levels of cardiac isoforms of SR Ca(2+)-ATPase (SERCA2a), phospholamban, calsequestrin, ryanodine receptor, and NCX were not significantly altered, but the SERCA2a-to-phospholamban ratio was increased 2.5-fold. Moreover, greater sensitivity to the inotropic effects of the beta-adrenoceptor agonist isoproterenol was observed in the PO-7d group. The results indicate enhanced Ca(2+) cycling between SR and cytosol early after PO imposition, even before hypertrophy development. Increase in SR Ca(2+) uptake may contribute to enhancement of excitation-contraction coupling (augmented SR Ca(2+) content and release) and protection against arrhythmogenesis due to buildup of [Ca(2+)](i) during diastole.
Subject: Animals
Calcium-binding Proteins
Calcium-transporting Atpases
Gene Expression Regulation
Hypertrophy, Left Ventricular
Myocardial Contraction
Myocytes, Cardiac
Rna, Messenger
Rats, Wistar
Sarcoplasmic Reticulum
Sarcoplasmic Reticulum Calcium-transporting Atpases
Signal Transduction
Citation: American Journal Of Physiology. Heart And Circulatory Physiology. v. 291, n. 4, p. H1803-13, 2006-Oct.
Rights: fechado
Identifier DOI: 10.1152/ajpheart.01345.2005
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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