Martin J F, Guth B D, Griffey R H, Hoekenga D E
Department of Radiology, University of California, San Diego Medical Center 92103.
Magn Reson Med. 1989 Jul;11(1):64-72. doi: 10.1002/mrm.1910110106.
In this study, we used 31P NMR to investigate the relationship between cardiac workload 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 T1 relaxation times for creatine phosphate and ATP which are longer than most reported values. Analysis of the T1 data indicates that chemical-shift anisotropy is a plausible mechanism for a portion of the spin-lattice relaxation rate at high field strengths.
在本研究中，我们使用³¹P核磁共振（NMR）来研究完整猪心脏的工作负荷与肌酸激酶通量之间的关系。对麻醉的小型猪进行NMR测量，通过手术在其左心室表面植入一个表面线圈。通过输注去甲肾上腺素来改变心脏工作负荷。磷酸肌酸和ATP之间的磷酸盐交换通过饱和转移和饱和恢复脉冲序列相结合的方法进行测量。交换测量结果表明，在心率-压力乘积变化2.5倍的范围内，肌酸激酶通量以及磷酸肌酸（PCr）和ATP的浓度与工作负荷无关。看来，如果肌酸激酶通量与工作负荷相关联，猪心脏在这样一种状态下运作：代谢物浓度或肌酸激酶通量的微小变化就足以维持较高的工作负荷。在2.0和4.7特斯拉的场强下进行的交换和弛豫测量，得到了磷酸肌酸和ATP的T1弛豫时间，这些时间比大多数报道的值要长。对T1数据的分析表明，在高场强下，化学位移各向异性是自旋-晶格弛豫率的一部分的一种合理机制。
