Abstract:
:Alternans in heart is important as pulsus alternans in cardiac failure and electrophysiological alternans in myocardial ischemia. The explanation of this phenomenon is still unclear. We attempted to investigate the cellular mechanisms of alternans by measuring intracellular free calcium concentration [( Ca2+]i) with the photoprotein aequorin in isolated ferret papillary muscles. Tension and length were also recorded simultaneously. Transient mechanical alternans lasting five to 20 contractions could be reliably induced in this preparation by following a 30-second rest period with stimulation at a fast rate (2-4 Hz). Production of sustained mechanical alternans, which lasted longer than 20 contractions and could persist for several hundred contractions, required additional interventions, consisting of a lower temperature (25 degrees C), a lower external calcium concentration (1 mM), and a lower pH (6.91) than control conditions (0.33-0.5 Hz, 30 degrees C, 2 mM Ca2+, pH 7.36). Transient mechanical alternans was associated with transient in-phase alternation of aequorin light and, hence, [Ca2+]i. Sustained mechanical alternans was associated with sustained in-phase alternation of aequorin light as well as incomplete relaxation of tension. However, when muscles were switched from isometric to unloaded isotonic contraction, relaxation between stimuli was complete but contraction and the aequorin light signal continued to alternate. The addition of 10 mM caffeine or 10 microns ryanodine abolished transient and sustained mechanical alternans and also abolished the associated alternation of aequorin light. Commensurate with the action of ryanodine, which allows the sarcoplasmic reticulum to reaccumulate calcium to a limited extent after a period of rapid stimulation, sustained mechanical alternans sometimes reappeared in an attenuated form 30 to 50 contractions after the addition of ryanodine. These results demonstrate that incomplete muscle relaxation between beats need not be present for alternans to occur, and support the hypothesis that alternans is caused by intracellular calcium cycling involving the sarcoplasmic reticulum.
journal_name
Circ Resjournal_title
Circulation researchauthors
Lab MJ,Lee JAdoi
10.1161/01.res.66.3.585subject
Has Abstractpub_date
1990-03-01 00:00:00pages
585-95issue
3eissn
0009-7330issn
1524-4571journal_volume
66pub_type
杂志文章abstract:RATIONALE:We previously discovered several phosphorylations to the beta subunit of the mitochondrial F(1)F(o) ATP synthase complex in isolated rabbit myocytes on adenosine treatment, an agent that induces cardioprotection. The role of these phosphorylations is unknown. OBJECTIVE:The present study focuses on the functi...
journal_title:Circulation research
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更新日期:2006-11-10 00:00:00
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更新日期:2021-01-08 00:00:00
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pub_type: 杂志文章
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更新日期:2007-05-25 00:00:00
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pub_type: 杂志文章,评审
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更新日期:2018-08-03 00:00:00
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pub_type: 杂志文章
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更新日期:1992-12-01 00:00:00
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journal_title:Circulation research
pub_type: 杂志文章,评审
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更新日期:2020-02-14 00:00:00
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journal_title:Circulation research
pub_type: 杂志文章
doi:10.1161/01.res.69.3.881
更新日期:1991-09-01 00:00:00
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pub_type: 杂志文章
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更新日期:1978-02-01 00:00:00
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pub_type: 杂志文章
doi:10.1161/01.res.60.2.177
更新日期:1987-02-01 00:00:00
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pub_type: 杂志文章,评审
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更新日期:2014-06-20 00:00:00
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更新日期:2015-07-03 00:00:00
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更新日期:2004-04-16 00:00:00
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pub_type: 杂志文章
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更新日期:2014-08-15 00:00:00
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journal_title:Circulation research
pub_type: 杂志文章
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更新日期:1991-07-01 00:00:00
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pub_type: 杂志文章
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更新日期:1995-01-01 00:00:00
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pub_type: 杂志文章
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更新日期:1990-10-01 00:00:00
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更新日期:1992-05-01 00:00:00
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更新日期:2002-07-26 00:00:00
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更新日期:2016-02-05 00:00:00
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更新日期:2009-05-08 00:00:00
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更新日期:2006-03-03 00:00:00