Flaherty J T, Weisfeldt M L, Bulkley B H, Gardner T J, Gott V L, Jacobus W E
Circulation. 1982 Mar;65(3):561-70. doi: 10.1161/01.cir.65.3.561.
Phosphorus-31 nuclear magnetic resonance (31P NMR) can estimate tissue intracellular pH as well as the content of high-energy phosphate metabolites in isolated perfused hearts. We used 31P NMR to examine mechanisms associated with the recovery of ventricular function in hearts subjected to global ischemia and reperfusion, with special emphasis on intracellular pH, a previously unreported variable. Single-dose and multiple-dose administration of a hyperkalemic cardioplegic solution were compared with hypothermia alone in 18 isolated perfused rabbit hearts. Hearts in group 1 were subjected to 24 degrees C hypothermia during 60 minutes of global ischemia; group 2 hearts received a single injection of 37-mM KCL cardioplegic solution at 10 degrees C at the onset of ischemia; and group 3 hearts received a similar initial cardioplegic injection followed by two subsequent 24 degrees C injections at 20-minute intervals during the ischemic period. Using an intraventricular balloon, maximal dP/dt provided a quantitative index of left ventricular performance before and after ischemia. Return of ventricular function expressed as a percentage of control was 54 +/- 11% for group 1, 84 +/- 6% for group 2, and 101 +/- 18% for group 3. Differences in the rate of development of intracellular acidosis were noted during the 60-minute ischemic period. Intracellular pH fell to 6.09 +/- 0.12 in group 1, 6.31 +/- 0.09 in group 2, an 6.79 +/- 0.03 in group 3. In all three groups intracellular pH returned to control (pH 7.20) within 10 minutes of reflow. The metabolic correlates of functional recovery appeared to be the tissue content of ATP at the end of ischemia and after reflow. ATP content at the end of ischemia was 22 +/- 2% of control in group 1 hearts, 31 +/- 4% in group 2 and 64 +/- 2% in group 3. After 45 minutes of reperfusion, ATP levels recovered to 33 +/- 9% of control in group 1, to 71 +/- 9% in group 2 and to 86 +/- 6% in group 3. Although there were no differences between groups in the content of creatine phosphate after 60 minutes of ischemia, the rates of creatine phosphate decline were dissimilar. Further, during the early reflow period, a marked overshoot in tissue creatine phosphate was detected, especially in groups 1 and 2. Histologic damage assessed by light microscopy correlated with the metabolic data, confirming that multidose cardioplegia provided the best preservation of cellular morphology. These results demonstrate that the magnitude of intracellular acidosis and the associated increase in inorganic phosphate correlate inversely with recovery of postischemic ventricular structure and function. ATP, but not creatine phosphate, content correlates with return of contractile performance after reperfusion. The overshoot in creatine phosphate during early reperfusion might impede optimal restoration of ATP content and, as a result, optimal recovery of cell functions.
磷-31核磁共振（31P NMR）可用于评估离体灌注心脏的组织细胞内pH值以及高能磷酸代谢物的含量。我们运用31P NMR来研究全心缺血再灌注心脏心室功能恢复的相关机制，特别关注细胞内pH值这一此前未被报道的变量。在18个离体灌注兔心脏中，将高钾心脏停搏液的单剂量和多剂量给药与单纯低温进行了比较。第1组心脏在60分钟全心缺血期间接受24℃低温处理；第2组心脏在缺血开始时于10℃接受单次37 mM KCl心脏停搏液注射；第3组心脏在缺血开始时接受类似的初始心脏停搏液注射，随后在缺血期间每隔20分钟进行两次24℃注射。使用心室内球囊，最大dP/dt提供了缺血前后左心室功能的定量指标。以对照组的百分比表示的心室功能恢复情况，第1组为54±11%，第2组为84±6%，第3组为101±18%。在60分钟缺血期内，观察到细胞内酸中毒发展速率的差异。第1组细胞内pH值降至6.09±0.12，第2组为6.31±0.09，第3组为6.79±0.03。在所有三组中，细胞内pH值在再灌注后10分钟内恢复至对照水平（pH 7.20）。功能恢复的代谢相关因素似乎是缺血末期和再灌注后组织中的ATP含量。第1组心脏缺血末期的ATP含量为对照的22±2%，第2组为31±4%，第3组为64±2%。再灌注45分钟后，第1组的ATP水平恢复至对照的33±9%，第2组为71±9%，第3组为86±6%。尽管缺血60分钟后各组之间磷酸肌酸含量无差异，但磷酸肌酸下降速率不同。此外，在早期再灌注期，检测到组织磷酸肌酸有明显的过冲现象，尤其是在第1组和第2组。通过光学显微镜评估的组织学损伤与代谢数据相关，证实多剂量心脏停搏液能最佳地保存细胞形态。这些结果表明，细胞内酸中毒的程度以及无机磷酸盐的相关增加与缺血后心室结构和功能的恢复呈负相关。ATP含量而非磷酸肌酸含量与再灌注后收缩功能的恢复相关。早期再灌注期间磷酸肌酸的过冲可能会阻碍ATP含量的最佳恢复，进而影响细胞功能的最佳恢复。
