In vivo measurement of myocardial protein turnover using an indicator dilution technique.
In vivo measurement of myocardial protein turnover using an indicator dilution technique.
复制标题
使用指示剂稀释技术体内测量心肌蛋白质周转率。
DOI：
10.1161/01.res.67.4.902
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发表时间：
1990
影响因子：
20.1
通讯作者：
Barrett,EJ
中科院分区：
文献类型：
--
作者：
Revkin,JH;Young,LH;Stirewalt,WS;Dahl,DM;Gelfand,RA;Zaret,BL;Barrett,EJ
我们将先前开发的用于测量骨骼肌蛋白质周转的非破坏性示踪技术应用于活体心肌蛋白质周转的测量。在给麻醉禁食犬持续输注L-[环-2，6-~3H]苯丙氨酸的过程中，我们用动脉和冠状静脉窦插管以及以前应用于骨骼肌的分析方法，测量了血浆对放射性标记苯丙氨酸的摄取和心肌蛋白分解中未标记苯丙氨酸的释放。使用这些测量，再加上一个心肌蛋白质合成模型，该模型假设心肌苯丙氨酰-tRNA和循环苯丙氨酸之间的示踪剂特定活性迅速平衡，我们估计了心脏蛋白质合成和降解率。通过将标记的苯丙氨酸掺入组织蛋白质中，直接估计心脏蛋白质合成的速率。本文比较了[~3H]苯丙氨酸和L-[1-14C]亮氨酸在同时输注这两种示踪剂的犬心脏蛋白质周转中的应用。心肌对亮氨酸的摄取和释放分别是苯丙氨酸的3.1+/-0.4-和1.7+/-0.3倍，与亮氨酸在心脏蛋白质及其通过其他途径的代谢中的2.4倍的丰度一致。苯丙氨酸是使用这种方法的首选示踪剂，因为它在肌肉中的代谢命运有限。该方法的一个理论局限性，即循环标记苯丙氨酸与心肌苯丙氨酰-tRNA的缓慢平衡，是通过比较大鼠注射标记苯丙氨酸30分钟后的这些特定活性来解决的。第二，经验上的限制涉及到测量苯丙氨酸比活度的精确度，苯丙氨酸比活度在每次血液通过冠脉循环时都会发生。这是通过提高苯丙氨酸浓度和苯丙氨酸比活度测量的精确度来解决的。我们的结论是，体内跨心肌苯丙氨酸示踪剂交换的测量可以非破坏性地估计完整动物的心脏蛋白质周转。
We applied a nondestructive tracer technique, previously developed for measuring skeletal muscle protein turnover, to the measurement of myocardial protein turnover in vivo. During a continuous infusion of L-[ring-2,6-3H]phenylalanine to anesthetized, overnight-fasted dogs, we measured the uptake of radiolabeled phenylalanine from plasma and the release of unlabeled phenylalanine from myocardial proteolysis using arterial and coronary sinus catheterization and analytic methods previously applied to skeletal muscle. Using these measurements, together with a model of myocardial protein synthesis that assumes rapid equilibration of tracer specific activity between myocardial phenylalanyl-tRNA and circulating phenylalanine, we estimated the rates of heart protein synthesis and degradation. The rate of heart protein synthesis was also estimated directly from the incorporation of labeled phenylalanine into tissue protein. The use of [3H]phenylalanine was compared with L-[1-14C]leucine in the measurement of heart protein turnover in dogs given simultaneous infusion of both tracers. Leucine uptake and release by the myocardium exceeded that of phenylalanine by 3.1 +/- 0.4- and 1.7 +/- 0.3-fold, respectively, consistent with leucine's 2.4-fold greater abundance in heart protein and its metabolism via other pathways. Phenylalanine is the preferred tracer for use with this method because of its limited metabolic fate in muscle. One theoretical limitation to the method, slow equilibration of circulating labeled phenylalanine with myocardial phenylalanyl-tRNA, was resolved by comparison of these specific activities after a 30-minute infusion of labeled phenylalanine in the rat. A second, empirical limitation involves precision in the measurement of the small decrements in phenylalanine specific activity that occur with each pass of blood through the coronary circulation. This was addressed by improving the precision of both the measurements of phenylalanine concentration and phenylalanine specific activity using high-performance liquid chromatography. We conclude that the in vivo measurement of phenylalanine tracer exchange across the myocardium permits the nondestructive estimation of heart protein turnover in the intact animal.