Reaction rates of creatine kinase and ATP synthesis in the isolated rat heart. A 31P NMR magnetization transfer study.
Authors
Discussion
Loading...
Member takes
Implication
Ex vivo study demonstrates that creatine kinase flux scales directly with oxygen consumption in isolated rat hearts, indicating tight coupling between myocardial energy production and transfer.
Key Points
- To determine the relationship between ATP synthesis and reaction flux through creatine kinase across varying levels of cardiac performance and oxygen consumption.
- Assessed isolated, isovolumic rat hearts across five distinct levels of cardiac workload and oxygen consumption.
- Measured unidirectional reaction rate constants and longitudinal relaxation times using phosphorus-31 nuclear magnetic resonance (31P NMR) magnetization transfer analyzed with a two-site exchange model.
- As cardiac rate-pressure product rose from 0 to 44.7 x 10^3 mm Hg/min and oxygen consumption increased from 5.9 to 45.8 μmol O2/g dry weight/min, kforward increased from 0.27 to 1.30 s^-1 and kreverse increased from 0.31 to 1.14 s^-1.
- Creatine kinase flux followed Michaelis-Menten kinetics relative to oxygen consumption, yielding ATP synthesis rates closely matching values derived from oxygen consumption.
- Longitudinal relaxation times remained constant across cardiac workloads for creatine phosphate (2.06 s), gamma-ATP (0.75 s), and inorganic phosphate (0.81 s).
Cite This Study
Bittl et al. (1985) studied this question.