期刊
BIOPHYSICAL JOURNAL
卷 93, 期 11, 页码 4083-4092出版社
CELL PRESS
DOI: 10.1529/biophysj.107.114546
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资金
- NHLBI NIH HHS [R01 HL074045, HL074045, R01 HL063043, HL063043] Funding Source: Medline
In this study, we investigated the role of elevated sarcoplasmic reticulum (SR) Ca2+ leak through ryanodine receptors (RyR2s) in heart failure (HF)-related abnormalities of intracellular Ca2+ handling, using a canine model of chronic HF. The cytosolic Ca2+ transients were reduced in amplitude and slowed in duration in HF myocytes compared with control, changes paralleled by a dramatic reduction in the total SR Ca2+ content. Direct measurements of [Ca2+] SR in both intact and permeabilized cardiac myocytes demonstrated that SR luminal [Ca2+] is markedly lowered in HF, suggesting that alterations in Ca2+ transport rather than fractional SR volume reduction accounts for the diminished Ca2+ release capacity of SR in HF. SR Ca2+ ATPase (SERCA2)-mediated SR Ca2+ uptake rate was not significantly altered, and Na+/Ca2+ exchange activity was accelerated in HF myocytes. At the same time, SR Ca2+ leak, measured directly as a loss of [Ca2+] SR after inhibition of SERCA2 by thapsigargin, was markedly enhanced in HF myocytes. Moreover, the reduced [Ca2+] SR in HF myocytes could be nearly completely restored by the RyR2 channel blocker ruthenium red. The effects of HF on cytosolic and SR luminal Ca2+ signals could be reasonably well mimicked by the RyR2 channel agonist caffeine. Taken together, these results suggest that RyR2-mediated SR Ca2+ leak is a major factor in the abnormal intracellular Ca2+ handling that critically contributes to the reduced SR Ca2+ content of failing cardiomyocytes.
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