title: Transmurally differentiated measurement of ATP hydrolysis rates in the in vivo porcine hearts.
abstract: OBJECTIVE
  Compare the transmural distribution of forward creatine kinase reaction (kf,CK ) and ATP hydrolysis rate (kr,ATPase ) in the myocardium of normal porcine heart. Rate constants were extracted from partially relaxed spectra by applying the T1nom method, effectively reducing data acquisition time by up to an order of magnitude.
  
  
  METHODS
  T1nom method for double saturation of PCr and Pi is introduced and validated through simulations. Bioenergetics was measured in vivo utilizing one-dimensional chemical shift imaging (1D-CSI) magnetic resonance (31) P spectroscopy.
  
  
  RESULTS
  At basal conditions, there was no significant difference between subepicardial layers (EPI) vs. the subendocardial layers (ENDO) for both fluxf,CK and fluxr,ATPase . At high cardiac workload (HWL), where the rate pressure product increased 2.6-fold, PCr/ATP ratio and fluxf,CK showed no significant change in both EPI and ENDO layers, while fluxr,ATPase increased significantly (baseline: 1.11 ± 0.12 and 1.12 ± 0.13 μmol/g/s, EPI and ENDO, respectively; to HWL: 2.35 ± 0.27 and 2.21 ± 0.08 μmol/g/s, EPI and ENDO, respectively, each P < 0.01 vs. baseline).
  
  
  CONCLUSIONS
  In the normal heart, increase of cardiac work state is accompanied by an increase in ATP hydrolysis rate with no changes in CK flux rate. There are no significant differences between EPI vs. ENDO concerning the ATP hydrolysis rate or CK flux rate in both baseline and high cardiac work states.
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota, USA.|Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, USA.|Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Jang
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xiong
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Pengyuan
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota, USA.|Department of Biomedical Engineering, School of Medicine, School of Engineering, UAB | The University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Jianyi
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D003198:Computer Simulation; D004699:Endocardium / Q000378:metabolism; D005260:Female; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics; D006868:Hydrolysis; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008962:Models, Theoretical; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010496:Pericardium / Q000378:metabolism; D013552:Swine
chemical_list: D000255:Adenosine Triphosphate; D010100:Oxygen
keywords: ATP hydrolysis rate; heart; high-energy phosphate; magnetic resonance spectroscopy; saturation transfer