title: Cardiac responses to β-adrenoceptor stimulation is partly dependent on mitochondrial calcium uniporter activity.
abstract: OBJECTIVE
  Despite the importance of mitochondrial Ca(2+) to metabolic regulation and cell physiology, little is known about the mechanisms that regulate Ca(2+) entry into the mitochondria. Accordingly, we established a system to determine the role of the mitochondrial Ca(2+) uniporter in an isolated heart model, at baseline and during increased workload following β-adrenoceptor stimulation.
  
  
  METHODS
  Cardiac contractility, oxygen consumption and intracellular Ca(2+) transients were measured in ex vivo perfused murine hearts. Ru360 and spermine were used to modify mitochondrial Ca(2+) uniporter activity. Changes in mitochondrial Ca(2+) content and energetic phosphate metabolite levels were determined.
  
  
  RESULTS
  The addition of Ru360 , a selective inhibitor of the mitochondrial Ca(2+) uniporter, induced progressively and sustained negative inotropic effects that were dose-dependent with an EC50 of 7 μM. Treatment with spermine, a uniporter agonist, showed a positive inotropic effect that was blocked by Ru360 . Inotropic stimulation with isoprenaline elevated oxygen consumption (2.7-fold), Ca(2+) -dependent activation of pyruvate dehydrogenase (5-fold) and mitochondrial Ca(2+) content (2.5-fold). However, in Ru360 -treated hearts, this parameter was attenuated. In addition, β-adrenoceptor stimulation in the presence of Ru360 did not affect intracellular Ca(2+) handling, PKA or Ca(2+) /calmodulin-dependent PK signalling.
  
  
  CONCLUSIONS
  Inhibition of the mitochondrial Ca(2+) uniporter decreases β-adrenoceptor response, uncoupling between workload and production of energetic metabolites. Our results support the hypothesis that the coupling of workload and energy supply is partly dependent on mitochondrial Ca(2+) uniporter activity.
authors.affiliation: Cátedra de Cardiología y Medicina Vascular, Escuela de Medicina, Tecnológico de Monterrey, Monterrey, Nuevo León, México.
authors.forename: E
authors.initials: E
authors.lastname: Fernández-Sada
authors.forename: C
authors.initials: C
authors.lastname: Silva-Platas
authors.forename: C A
authors.initials: CA
authors.lastname: Villegas
authors.forename: S L
authors.initials: SL
authors.lastname: Rivero
authors.forename: B C
authors.initials: BC
authors.lastname: Willis
authors.forename: N
authors.initials: N
authors.lastname: García
authors.forename: J R
authors.initials: JR
authors.lastname: Garza
authors.forename: Y
authors.initials: Y
authors.lastname: Oropeza-Almazán
authors.forename: C A
authors.initials: CA
authors.lastname: Valverde
authors.forename: G
authors.initials: G
authors.lastname: Mazzocchi
authors.forename: C
authors.initials: C
authors.lastname: Zazueta
authors.forename: G
authors.initials: G
authors.lastname: Torre-Amione
authors.forename: G
authors.initials: G
authors.lastname: García-Rivas
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008929:Mitochondria, Heart / Q000187:drug effects / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D010101:Oxygen Consumption; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D017975:Ruthenium Compounds / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D000099211:Phospholamban
chemical_list: D000318:Adrenergic beta-Agonists; D002118:Calcium; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D002316:Cardiotonic Agents; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D005978:Glutathione; D007545:Isoproterenol; D011943:Receptors, Adrenergic, beta; D017975:Ruthenium Compounds; D013096:Spermine; D000099211:Phospholamban; C112020:Ru 360; C034703:mitochondrial calcium uniporter