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Subcellular Ca 2+ alternans represents a novel mechanism for the generation of arrhythmogenic Ca 2+ waves in cat atrial myocytes
Author(s) -
Kockskämper Jens,
Blatter Lothar A.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.025502
Subject(s) - myocyte , endoplasmic reticulum , biophysics , subcellular localization , glycolysis , contraction (grammar) , stimulation , medicine , chemistry , biology , microbiology and biotechnology , endocrinology , metabolism , cytoplasm
Ca 2+ alternans is a potentially arrhythmogenic beat‐to‐beat alternation of the amplitude of the action potential‐induced [Ca 2+ ] i transient in cardiac myocytes. Despite its pathophysiological significance the cellular mechanisms underlying Ca 2+ alternans are poorly understood. Recent evidence, however, points to the modulation of Ca 2+ ‐induced Ca 2+ release (CICR) from the sarcoplasmic reticulum (SR) by localized alterations in energy metabolism as an important determinant of Ca 2+ alternans. We therefore studied the subcellular properties of Ca 2+ alternans in field‐stimulated cat atrial myocytes employing fast two‐dimensional fluorescence confocal microscopy. Ca 2+ alternans was elicited by an increase in stimulation frequency or by metabolic interventions targeting glycolysis. Marked subcellular variations in the time of onset, the magnitude, and the phase of alternans were observed. Longitudinal and transverse gradients of Ca 2+ alternans were found as well as neighbouring subcellular regions alternating out‐of‐phase. Moreover, focal inhibition of glycolysis resulted in spatially restricted Ca 2+ alternans. When two adjacent regions within a myocyte alternated out‐of‐phase, steep [Ca 2+ ] i gradients developed at their border giving rise to delayed propagating Ca 2+ waves. The results demonstrate that Ca 2+ alternans is a subcellular phenomenon caused by modulation of SR Ca 2+ release, which is mediated, at least in part, by local inhibition of energy metabolism. The generation of arrhythmogenic Ca 2+ waves by subcellular variations in the phase of Ca 2+ alternans represents a novel mechanism for the development of atrial disrhythmias.