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Myocardial creatine kinase exchange rates and 31 P NMR relaxation rates in intact pigs
Author(s) -
Martin Joel F.,
Guth Brian D.,
Griffey Richard H.,
Hoekenga David E.
Publication year - 1989
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910110106
Subject(s) - creatine , creatine kinase , ventricle , chemistry , spin–lattice relaxation , phosphocreatine , nuclear magnetic resonance spectroscopy , spin–spin relaxation , nuclear magnetic resonance , medicine , biochemistry , stereochemistry , physics , nuclear quadrupole resonance , energy metabolism
In this study, we used 31 P NMR to investigate the relationship between cardiac work load and creatine kinase flux in intact pigs. NMR measurements were performed on anesthetized miniature swine in which a surface coil was surgically implanted on the surface of the left ventricle. Cardiac workload was varied by infusion of norepinephrine. Phosphate exchange between creatine phosphate and ATP was measured by a combined saturation transfer, saturation recovery pulse sequence. Exchange measurements showed that creatine kinase flux and concentrations of PCr and ATP were independent of workload for a 2.5‐fold range of cardiac rate‐pressure products. It appears that, if creatine kinase flux is coupled to work load, the pig heart operates in a regime where small changes in metabolite concentrations or creatine kinase flux are sufficient to maintain elevated workloads. Exchange and relaxation measurements, at 2.0 and 4.7 T, yielded T 1 relaxation times for creatine phosphate and ATP which are longer than most reported values. Analysis of the T 1 data indicates that chemical‐shift anisotropy is a plausible mechanism for a portion of the spin‐lattice relaxation rate at high field strengths. © 1989 Academic Press. Inc.