Mitochondrial free calcium transients during excitation-contraction coupling in rabbit cardiac myocytes

Enrique Chacon, Hisayuki Ohata, Ian S. Harper, Donna R. Trollinger, Brian Herman, John J. Lemasters

Research output: Contribution to journalArticlepeer-review

94 Scopus citations


Mitochondrial free Ca2+ may regulate mitochondrial ATP production during cardiac exercise. Here, using laser scanning confocal microscopy of adult rabbit cardiac myocytes co-loaded with Fluo-3 to measure free Ca2+ and tetramethylrhodamine methylester to identify mitochondria, we measured cytosolic and mitochondrial Ca2+ transients during the contractile cycle. In resting cells, cytosolic and mitochondrial Fluo-3 signals were similar. During electrical pacing, transients of Fluo-3 fluorescence occurred in both the cytosolic and mitochondrial compartments. Both the mitochondrial and the cytosolic transients were potentiated by isoproterenol. These experiments show directly that mitochondrial free Ca2+ rises and falls during excitation-contraction coupling in cardiac myocytes and that changes of mitochondrial Ca2+ are kinetically competent to regulate mitochondrial metabolism on a beat-to-beat basis.

Original languageEnglish (US)
Pages (from-to)31-36
Number of pages6
JournalFEBS Letters
Issue number1-2
StatePublished - Mar 11 1996

Bibliographical note

Funding Information:
Acknowledgements: We thank Mr. Jeffrey M. Reece, Mr. Samuel A. Tesfai and Dr. Ammasi Periasamy for expert technical assistance. This work was supported, in part, by Grant HL48769 from the National Institutes of Health. E.C. was the recipient of a National Research Service Award from the National Institute of Environmental Health Sciences through Grant T32ES07126 to the Curriculum in Toxicology. I.S.H. was the recipient of a Post-Doctoral Scholarship from the Medical Research Council of South Africa. Portions of this work were presented at the 37th Annual Meeting of the Biophysical Society, 14-18 February 1993 in Washington, DC \[39\]a nd the 67th Scientific Sessions of the American Heart Association, 14-17 November 1994 in Dallas, Texas \[40\].


  • Calcium
  • Confocal microscopy
  • Excitation-contraction coupling
  • Mitochondria
  • Myocyte


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