Lewandowski E D, Johnston D L, Roberts R
Department of Medicine, Baylor College of Medicine, Houston, TX 77030.
Circ Res. 1991 Feb;68(2):578-87. doi: 10.1161/01.res.68.2.578.
The effects of inosine (INO) on substrate metabolism and rigor formation in ischemic myocardium were examined in isolated rabbit hearts. Metabolite content was assessed in tissue extracts by chemical analysis and in the whole heart by 13C and 31P nuclear magnetic resonance spectroscopy. In ischemic hearts metabolizing either [3-13C]pyruvate or [1-13C]glucose, 1 mM INO increased both total and 13C-labeled alanine content; lactate content was unaffected. At 3 minutes of ischemia, tissue alanine was 1.81 +/- 0.11 microM/g wet wt (mean +/- SEM) in hearts perfused with pyruvate+INO versus 1.23 +/- 0.15 microM/g wet wt in hearts perfused with pyruvate alone (p less than 0.05). INO reduced tissue glycogen during ischemia in pyruvate-perfused hearts. Tissue alanine content in ischemic hearts that were supplied glucose+INO (1.29 +/- 0.13 microM/g wet wt) was greater than in ischemic hearts supplied glucose alone (0.65 +/- 0.14 microM/g wet wt). Alanine was found to originate from pyruvate and was a glycolytic end product in glucose-perfused hearts. INO raised the [3-13C]alanine/[3-13C]lactate ratio in ischemic, intact hearts (glucose = 0.24 +/- 0.07 versus glucose+INO = 0.60 +/- 0.09; pyruvate = 0.49 +/- 0.08 versus pyruvate+INO = 0.89 +/- 0.08). At 7 minutes of ischemia, ATP content fell to 70 +/- 3% with glucose+INO versus 58 +/- 5% with glucose alone. Rigor (stone heart) was delayed from 14.7 +/- 1.3 to 23.2 +/- 1.6 minutes with INO. INO did not change ATP content in ischemic hearts that were supplied pyruvate but delayed rigor (pyruvate = 9.9 +/- 1.2 minutes; pyruvate+INO = 15.6 +/- 1.0 minutes), possibly at the expense of glycogen. Supplemental glucose improved the effectiveness of INO with pyruvate to preserve ATP (pyruvate+glucose = 42 +/- 6%; pyruvate+glucose+INO = 72 +/- 6%) and further delayed rigor (pyruvate+glucose = 13.3 +/- 1.5 minutes; pyruvate+glucose+INO = 20.3 +/- 1.8 minutes). Glucose metabolism supported improved energetic and contractile states in ischemic hearts treated with INO. Thus, cardioprotection of the ischemic heart by INO was associated with preservation of functional integrity and improved energy production due to increased glycolytic activity. Activation of glycolysis in the presence of INO was accommodated by augmented alanine production without the additional accumulation of lactate.
在离体兔心脏中研究了肌苷（INO）对缺血心肌底物代谢和僵硬度形成的影响。通过化学分析评估组织提取物中的代谢物含量，并通过13C和31P核磁共振波谱评估整个心脏中的代谢物含量。在代谢[3-13C]丙酮酸或[1-13C]葡萄糖的缺血心脏中，1 mM INO增加了总丙氨酸含量和13C标记的丙氨酸含量；乳酸含量未受影响。在缺血3分钟时，灌注丙酮酸+INO的心脏中组织丙氨酸含量为1.81±0.11μM/g湿重（平均值±标准误），而仅灌注丙酮酸的心脏中为1.23±0.15μM/g湿重（p<0.05）。INO降低了丙酮酸灌注心脏缺血期间的组织糖原含量。供应葡萄糖+INO的缺血心脏中的组织丙氨酸含量（1.29±0.13μM/g湿重）高于仅供应葡萄糖的缺血心脏（0.65±0.14μM/g湿重）。发现丙氨酸来源于丙酮酸，并且是葡萄糖灌注心脏中的糖酵解终产物。INO提高了缺血完整心脏中[3-13C]丙氨酸/[3-13C]乳酸的比值（葡萄糖组=0.24±0.07，葡萄糖+INO组=0.60±0.09；丙酮酸组=0.49±0.08，丙酮酸+INO组=0.89±0.08）。在缺血7分钟时，葡萄糖+INO组的ATP含量降至70±3%，而葡萄糖组为58±5%。INO使僵硬度（石心）从14.7±1.3分钟延迟至23.2±1.6分钟。INO未改变供应丙酮酸的缺血心脏中的ATP含量，但延迟了僵硬度（丙酮酸组=9.9±1.2分钟；丙酮酸+INO组=15.6±1.0分钟），可能是以糖原消耗为代价。补充葡萄糖提高了INO与丙酮酸联合保存ATP的有效性（丙酮酸+葡萄糖组=42±6%；丙酮酸+葡萄糖+INO组=72±6%），并进一步延迟了僵硬度（丙酮酸+葡萄糖组=13.3±1.5分钟；丙酮酸+葡萄糖+INO组=20.3±1.8分钟）。葡萄糖代谢支持了INO治疗的缺血心脏中能量和收缩状态的改善。因此，INO对缺血心脏的心脏保护作用与功能完整性的保存以及由于糖酵解活性增加而改善的能量产生有关。在INO存在下糖酵解的激活通过增加丙氨酸产生而实现，而没有额外的乳酸积累。
