Document Detail

Characterization of junctional sarcoplasmic reticulum Ca2+ content and release by short-term mechanical restitution in cardiac muscle.
MedLine Citation:
PMID:  15541199     Owner:  NLM     Status:  MEDLINE    
To study Ca2+ handling by the junctional sarcoplasmic reticulum (JSR), the time course of short-term mechanical restitution after varying magnitudes of twitch contractions was assessed in rat papillary muscle. Mechanical restitution consisted of a pretwitch latency period followed by a rapid and a subsequent much slower restitution of twitch force. The rate of rapid restitution was independent of the magnitude of the preceding twitch, which suggests that the rate of JSR Ca2+ repletion was dependent on the amount of Ca2+ remaining in the JSR after a twitch contraction. Based on this finding, the functions Gt and Ht, representing the time courses of JSR Ca2+ repletion and release, respectively, were derived graphically from a family of the mechanical restitution curves. Gt increased monotonically with time at a decreasing rate, while Ht increased with time in a sigmoid manner. The mechanical alternans were simulated by using experimental values and mathematically predicted values of Gt and Ht. A substitution of extracellular Na+ with Li+ to inhibit Na+/Ca2+ exchange resulted in an augmentation of Gt by approximately 10%, presumably by increasing the tubular SR Ca2+ uptake. The inhibition of tubular SR Ca2+ uptake by thapsigargin (10 microM) reduced mechanical restitution by approximately 13% of the maximal twitch force, independent of the phase of mechanical restitution; the effect was greater at an earlier time point in the mechanical restitution. These results suggest that early JSR Ca2+ replenishment results mainly from the movement of Ca2+ from the tubular SR.
T Tameyasu; M Tanaka; S Ogura; M Sato
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  The Japanese journal of physiology     Volume:  54     ISSN:  0021-521X     ISO Abbreviation:  Jpn. J. Physiol.     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-11-15     Completed Date:  2005-04-12     Revised Date:  2007-03-21    
Medline Journal Info:
Nlm Unique ID:  2985184R     Medline TA:  Jpn J Physiol     Country:  Japan    
Other Details:
Languages:  eng     Pagination:  209-19     Citation Subset:  IM    
Department of Physiology, St. Marianna University School of Medicine, Miyamae-ku, Kawasaki, 216-8511 Japan.
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MeSH Terms
Adaptation, Physiological / physiology
Calcium / metabolism*
Calcium Signaling / physiology*
Computer Simulation
Models, Cardiovascular*
Myocardial Contraction / drug effects,  physiology*
Papillary Muscles / drug effects,  physiology*
Rats, Wistar
Sarcoplasmic Reticulum / drug effects,  physiology*
Sodium-Calcium Exchanger / physiology
Stress, Mechanical
Thapsigargin / pharmacology
Reg. No./Substance:
0/Sodium-Calcium Exchanger; 67526-95-8/Thapsigargin; 7440-70-2/Calcium

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