Ca(2+) release from the sarcoplasmic reticulum activated by the low affinity Ca(2+) chelator TPEN in ventricular myocytes

Jung, C; Zima, A V; Szentesi, P; Jona, I; Blatter, L A; Niggli, E (2007). Ca(2+) release from the sarcoplasmic reticulum activated by the low affinity Ca(2+) chelator TPEN in ventricular myocytes. Cell calcium, 41(2), pp. 187-94. Amsterdam: Elsevier 10.1016/j.ceca.2006.06.009

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The Ca(2+) content of the sarcoplasmic reticulum (SR) of cardiac myocytes is thought to play a role in the regulation and termination of SR Ca(2+) release through the ryanodine receptors (RyRs). Experimentally altering the amount of Ca(2+) within the SR with the membrane-permeant low affinity Ca(2+) chelator TPEN could improve our understanding of the mechanism(s) by which SR Ca(2+) content and SR Ca(2+) depletion can influence Ca(2+) release sensitivity and termination. We applied laser-scanning confocal microscopy to examine SR Ca(2+) release in freshly isolated ventricular myocytes loaded with fluo-3, while simultaneously recording membrane currents using the whole-cell patch-clamp technique. Following application of TPEN, local spontaneous Ca(2+) releases increased in frequency and developed into cell-wide Ca(2+) waves. SR Ca(2+) load after TPEN application was found to be reduced to about 60% of control. Isolated cardiac RyRs reconstituted into lipid bilayers exhibited a two-fold increase of their open probability. At the low concentration used (20-40muM), TPEN did not significantly inhibit the SR-Ca(2+)-ATPase in SR vesicles. These results indicate that TPEN, traditionally used as a low affinity Ca(2+) chelator in intracellular Ca(2+) stores, may also act directly on the RyRs inducing an increase in their open probability. This in turn results in an increased Ca(2+) leak from the SR leading to its Ca(2+) depletion. Lowering of SR Ca(2+) content may be a mechanism underlying the recently reported cardioprotective and antiarrhythmic features of TPEN.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Physiology
UniBE Contributor:	Jung, Carole, Niggli, Ernst
ISSN:	0143-4160
ISBN:	16920191
Publisher:	Elsevier
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:45
Last Modified:	05 Dec 2022 14:13
Publisher DOI:	10.1016/j.ceca.2006.06.009
PubMed ID:	16920191
Web of Science ID:	000244167500009
URI:	https://boris.unibe.ch/id/eprint/18503 (FactScience: 666)