Bhattacharya Pratip, Ross Brian D, Bünger Rolf
Enhanced MR Laboratory, Huntington Medical Research Institutes, 10 Pico Street, Pasadena, CA 91105.
Exp Biol Med (Maywood). 2009 Dec;234(12):1395-416. doi: 10.3181/0904-MR-135.
Modern hyperpolarization technology enhances the recordable magnetic resonance signal four to five orders of magnitude, making in vivo assessments of tracer pathways and metabolic compartments feasible. Existing hyperpolarization instrumentation and previous tracer studies using hydroxyethylpropionate (HEP) as an extracellular marker and 14-carbon label pyruvate as examples are described and reviewed as applicable to the working heart. Future metabolic imaging based on the use of hyperpolarized pyruvate needs to consider extra- and intra-cellular label dilution due to glycolysis, lactate oxidation and protein degradation. This dilution can substantially decrease the recordable signals from PDH flux (oxidative decarboxylation of pyruvate) and other pyruvate pathways. The review of previous literature and data suggests that the (13)C-alanine signal is a better index of mitochondrially oxidized pyruvate than L-lactate. These facts and considerations will help in the interpretation of the in vivo recorded hyperpolarization signals of metabolic tracers and contrast media.
现代超极化技术将可记录的磁共振信号增强了四到五个数量级，使得对示踪剂途径和代谢区室进行体内评估成为可能。现有的超极化仪器以及先前以羟乙基丙酸酯（HEP）作为细胞外标记物和14碳标记丙酮酸为例的示踪剂研究，在适用于工作心脏的情况下进行了描述和综述。未来基于超极化丙酮酸的代谢成像需要考虑由于糖酵解、乳酸氧化和蛋白质降解导致的细胞外和细胞内标记物稀释。这种稀释会显著降低来自丙酮酸脱氢酶通量（丙酮酸的氧化脱羧）和其他丙酮酸途径的可记录信号。对先前文献和数据的综述表明，与L-乳酸相比，（13）C-丙氨酸信号是线粒体氧化丙酮酸的更好指标。这些事实和考虑因素将有助于解释代谢示踪剂和造影剂在体内记录的超极化信号。
