title: Mitochondrial free calcium transients during excitation-contraction coupling in rabbit cardiac myocytes.
abstract: 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.
authors.affiliation: Department of Cell Biology & Anatomy and Curriculum in Toxicology, School of Medicine, University of North Carolina at Chapel Hill, NC 27599-7090, USA.
authors.forename: E
authors.initials: E
authors.lastname: Chacon
authors.forename: H
authors.initials: H
authors.lastname: Ohata
authors.forename: I S
authors.initials: IS
authors.lastname: Harper
authors.forename: D R
authors.initials: DR
authors.lastname: Trollinger
authors.forename: B
authors.initials: B
authors.lastname: Herman
authors.forename: J J
authors.initials: JJ
authors.lastname: Lemasters
mesh_terms: D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004558:Electric Stimulation; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000378:metabolism*; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism*; D011817:Rabbits; D012235:Rhodamines; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; D005452:Fluoresceins; D005456:Fluorescent Dyes; D012235:Rhodamines; D014966:Xanthenes; C085925:calcein AM; C059715:Fluo-3; C005358:tetramethylrhodamine; D002118:Calcium