Linked Life Data

8383504

Source:http://linkedlifedata.com/resource/pubmed/id/8383504

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1993-4-15
pubmed:abstractText
These experiments analyse the phase-dependent properties of spontaneous oscillations of the sarcoplasmic reticulum (SR) induced by Ca2+ overload. Right atrial tissue was loaded with intracellular Ca2+ by exposure to a modified Tyrode solution containing 50% of normal Na+ and 0.5 mM K+. Verapamil (2 microM) was added to block regenerative activity. Intracellular Ca2+ overload elicited spontaneous, rhythmic voltage and tension oscillations that were phase locked 1:1. Voltage and tension oscillations were abolished by exposure to low (0.9 mM) external Ca2+, 1 microM ryanodine, or 10 mM caffeine, indicating that both voltage and tension oscillations resulted from spontaneous oscillations in SR Ca2+ release. Single pulses of nerve-stimulated ACh release elicited phase shifts in both voltage and tension oscillations. Sinusoidal current was used as a periodic stimulus to drive membrane voltage and elicit periodic voltage oscillations. Stimulated voltage oscillations entrained spontaneous tension oscillations 1:1 in a range of frequencies close to the basic spontaneous SR oscillatory cycle length, or 2:1 at frequencies close to one-half the spontaneous SR oscillatory cycle length. Stimulation frequencies between these two regions entrained tension oscillations in predictable fixed coupled ratios (4:3, 3:2) and resulted in Wenckeback-like voltage patterns. Stimulation frequencies between phase-locked regions resulted in complex coupling relationships and irregular voltage patterns. Exposure to 1 microM ryanodine, 0.9 mM external Ca2+, or 10 mM caffeine abolished irregular voltage patterns and tension. We conclude that the SR oscillator exhibits phase-dependent sensitivity to perturbations at the surface membrane. As a result, external perturbations can elicit phase differences between spontaneous SR oscillations and membrane voltage that cause either phase-locked or irregular voltage patterns. These findings identify an intracellular mechanism that may contribute to the development of cardiac dysrhythmias resulting from intracellular Ca2+ overload.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0958-0670
pubmed:author
pubmed:issnType
Print
pubmed:volume
78
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
79-93
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Phase-dependent properties of the cardiac sarcoplasmic reticulum oscillator in cat right atrium: a mechanism contributing to dysrhythmias induced by Ca2+ overload.
pubmed:affiliation
Department of Physiology, Loyola University of Chicago, Stritch School of Medicine, Maywood, IL 60153.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S.