Chua B, Siehl D L, Fuller E O, Morgan H E
Adv Myocardiol. 1983;4:115-25. doi: 10.1007/978-1-4757-4441-5_9.
The purpose of these experiments was to assess effects of cardiac work and leucine in hearts supplied only glucose or substrate and hormone mixtures that simulated plasma. Rates of protein degradation greatly exceeded protein synthesis in Langendorff preparations supplied glucose. This severely negative nitrogen balance was brought closer to zero by provision of more complete substrate mixtures. Cardiac work further improved the nitrogen balance by stimulating protein synthesis in hearts supplied glucose (mixture 1), glucose-insulin-glucagon-lactate-beta-hydroxybutyrate (mixture 2), or palmitate-beta-hydroxybutyrate-glucose (mixture 3) and inhibiting protein degradation in hearts supplied glucose. Cardiac work did not affect the rates of either protein synthesis or degradation in hearts provided insulin-lactate-glucose (mixture 4). The increase in protein synthesis was associated with increased rates of peptide chain initiation. Addition of 1 mM leucine had an additional effect to restore nitrogen balance to zero or to achieve positive balance in working hearts supplied substrate and hormone mixture 2.
这些实验的目的是评估心脏工作以及亮氨酸对仅供应葡萄糖或模拟血浆的底物与激素混合物的心脏的影响。在供应葡萄糖的Langendorff标本中，蛋白质降解速率大大超过蛋白质合成速率。通过提供更完整的底物混合物，这种严重的负氮平衡更接近零。心脏工作通过刺激供应葡萄糖（混合物1）、葡萄糖 - 胰岛素 - 胰高血糖素 - 乳酸 - β - 羟基丁酸（混合物2）或棕榈酸酯 - β - 羟基丁酸 - 葡萄糖（混合物3）的心脏中的蛋白质合成，并抑制供应葡萄糖的心脏中的蛋白质降解，进一步改善了氮平衡。心脏工作对供应胰岛素 - 乳酸 - 葡萄糖（混合物4）的心脏中的蛋白质合成或降解速率没有影响。蛋白质合成的增加与肽链起始速率的增加有关。添加1 mM亮氨酸具有额外的作用，可使供应底物和激素混合物2的工作心脏中的氮平衡恢复到零或实现正平衡。
