Luminal Ca2+ content regulates intracellular Ca2+ release in subepicardial myocytes of intact beating mouse hearts: effect of exogenous buffers
Ca + -induced Ca 2+ release tightly controls the function of ventricular cardiac myocytes under normal and pathological conditions. Two major factors contributing to the regulation of Ca 2+ release are the cytosolic free Ca 2+ concentration and sarcoplasmic reticulum (SR) Ca 2+ content. We hypothesi...
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Published in | American journal of physiology. Heart and circulatory physiology Vol. 298; no. 6; pp. H2138 - H2153 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Bethesda, MD
American Physiological Society
01.06.2010
|
Online Access | Get full text |
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Summary: | Ca
+
-induced Ca
2+
release tightly controls the function of ventricular cardiac myocytes under normal and pathological conditions. Two major factors contributing to the regulation of Ca
2+
release are the cytosolic free Ca
2+
concentration and sarcoplasmic reticulum (SR) Ca
2+
content. We hypothesized that the amount of Ca
2+
released from the SR during each heart beat strongly defines the refractoriness of Ca
2+
release. To test this hypothesis, EGTA AM, a high-affinity, slow-association rate Ca
2+
chelator, was used as a tool to modify luminal SR Ca
2+
content. An analysis of the cytosolic and luminal SR Ca
2+
dynamics recorded from the epicardial layer of intact mouse hearts indicated that the presence of EGTA reduced the diastolic SR free Ca
2+
concentration and fraction of SR Ca
2+
depletion during each beat. In addition, this maneuver shortened the refractory period and accelerated the restitution of Ca
2+
release. As a consequence of the accelerated restitution, the frequency dependence of Ca
2+
alternans was significantly shifted toward higher heart rates, suggesting a role of luminal SR Ca
2+
in the genesis of this highly arrhythmogenic phenomenon. Thus, intra-SR Ca
2+
dynamics set the refractoriness and frequency dependence of Ca
2+
transients in subepicardial ventricular myocytes. |
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ISSN: | 0363-6135 1522-1539 |
DOI: | 10.1152/ajpheart.00885.2009 |