title: Cardiac, skeletal, and smooth muscle mitochondrial respiration: are all mitochondria created equal?
abstract: Unlike cardiac and skeletal muscle, little is known about vascular smooth muscle mitochondrial respiration. Therefore, the present study examined mitochondrial respiratory rates in smooth muscle of healthy human feed arteries and compared with that of healthy cardiac and skeletal muscles. Cardiac, skeletal, and smooth muscles were harvested from a total of 22 subjects (53 ± 6 yr), and mitochondrial respiration was assessed in permeabilized fibers. Complex I + II, state 3 respiration, an index of oxidative phosphorylation capacity, fell progressively from cardiac to skeletal to smooth muscles (54 ± 1, 39 ± 4, and 15 ± 1 pmol·s(-1)·mg(-1), P < 0.05, respectively). Citrate synthase (CS) activity, an index of mitochondrial density, also fell progressively from cardiac to skeletal to smooth muscles (222 ± 13, 115 ± 2, and 48 ± 2 μmol·g(-1)·min(-1), P < 0.05, respectively). Thus, when respiration rates were normalized by CS (respiration per mitochondrial content), oxidative phosphorylation capacity was no longer different between the three muscle types. Interestingly, complex I state 2 normalized for CS activity, an index of nonphosphorylating respiration per mitochondrial content, increased progressively from cardiac to skeletal to smooth muscles, such that the respiratory control ratio, state 3/state 2 respiration, fell progressively from cardiac to skeletal to smooth muscles (5.3 ± 0.7, 3.2 ± 0.4, and 1.6 ± 0.3 pmol·s(-1)·mg(-1), P < 0.05, respectively). Thus, although oxidative phosphorylation capacity per mitochondrial content in cardiac, skeletal, and smooth muscles suggest all mitochondria are created equal, the contrasting respiratory control ratio and nonphosphorylating respiration highlight the existence of intrinsic functional differences between these muscle mitochondria. This likely influences the efficiency of oxidative phosphorylation and could potentially alter ROS production.
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah;
authors.forename: Song-Young
authors.initials: SY
authors.lastname: Park
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah;
authors.forename: Jayson R
authors.initials: JR
authors.lastname: Gifford
authors.affiliation: Department of Surgery, Huntsman Cancer Hospital, University of Utah, Salt Lake City, Utah;
authors.forename: Robert H I
authors.initials: RH
authors.lastname: Andtbacka
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah;
authors.forename: Joel D
authors.initials: JD
authors.lastname: Trinity
authors.affiliation: Department of Surgery, Huntsman Cancer Hospital, University of Utah, Salt Lake City, Utah;
authors.forename: John R
authors.initials: JR
authors.lastname: Hyngstrom
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah;
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Garten
authors.affiliation: Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, Utah;
authors.forename: Nikolaos A
authors.initials: NA
authors.lastname: Diakos
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah; Health and Exercise Sciences Department, Skidmore College, Saratoga Springs, New York.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ives
authors.affiliation: Department of Biomedical Sciences, Copenhagen University, Copenhagen, Denmark; and.
authors.forename: Flemming
authors.initials: F
authors.lastname: Dela
authors.affiliation: Department of Biomedical Sciences, Copenhagen University, Copenhagen, Denmark; and.
authors.forename: Steen
authors.initials: S
authors.lastname: Larsen
authors.affiliation: Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, Utah;
authors.forename: Stavros
authors.initials: S
authors.lastname: Drakos
authors.affiliation: Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah; Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah; r.richardson@hsc.utah.edu.
authors.forename: Russell S
authors.initials: RS
authors.lastname: Richardson
mesh_terms: D019069:Cell Respiration; D002950:Citrate (si)-Synthase / Q000378:metabolism; D042967:Electron Transport Complex I / Q000378:metabolism; D042963:Electron Transport Complex II / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008929:Mitochondria, Heart / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010641:Phenotype
chemical_list: D042963:Electron Transport Complex II; D002950:Citrate (si)-Synthase; D042967:Electron Transport Complex I
keywords: feed arteries; oxidative phosphorylation capacity; respiratory control ratio