Oxidation of branched chain amino acids by isolated hearts and diaphragms of the rat. The effect of fatty acids, glucose, and pyruvate respiration.
Oxidation of branched chain amino acids by isolated hearts and diaphragms of the rat. The effect of fatty acids, glucose, and pyruvate respiration.
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大鼠离体心脏和隔膜对支链氨基酸的氧化。
DOI：
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发表时间：
1972
影响因子：
4.8
通讯作者：
J. Buse
中科院分区：
文献类型：
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作者：
M. Buse;J. F. Biggers;K. Friderici;J. Buse
本文研究了自由进食大鼠灌流心脏和离体培养膈肌的氨基酸氧化。用含有葡萄糖和0.1 mM氨基酸的Krebs-Henseleit碳酸氢盐缓冲液灌注心脏。向培养基中添加1 mm辛酸盐显著刺激[1- 14 C]亮氨酸、异亮氨酸和缬氨酸产生14 CO2;抑制[1 - 14 C]丙氨酸、丙酮酸和α-酮戊二酸产生14 CO2，而不影响[14 C]组氨酸、苏氨酸、谷氨酸、鸟氨酸和苯丙氨酸产生14 CO2。与1 mm己酸或0.1至1.0 mm辛酸孵育的半隔膜增加了80%至200%的支链氨基酸的氧化，并降低了丙氨酸和丙酮酸的14 CO2生产。辛酸刺激异亮氨酸的氧化半隔膜在异亮氨酸浓度为0.01至1.0毫米之间，当异亮氨酸超过2毫米，辛酸成为抑制。辛酸刺激氧化的支链氨基酸在存在或不存在葡萄糖和存在或不存在胰岛素从介质中，在隔膜和心脏。牛血清白蛋白不影响支链氨基酸氧化的情况下添加脂肪酸，它抑制了后者的刺激作用。抑制作用与白蛋白浓度成正比。棕榈酸酯和油酸酯（1毫米）加入白蛋白（15毫克每毫升）刺激支链氨基酸氧化的hemidiaphragms;效果小于观察到的等摩尔辛酸和白蛋白。在心脏中，未观察到1 mm棕榈酸盐的影响。丁酸盐（2 mm）不影响侧膈对支链氨基酸的氧化; 4 mm dl-β-OH丁酸盐和4 mm乙酸盐具有抑制作用。在心脏和横膈膜中，培养液中葡萄糖的缺失刺激了支链氨基酸的氧化。丙酮酸加入到含有葡萄糖的培养基中引起支链氨基酸氧化的进一步抑制。在禁食48小时和无葡萄糖灌注的大鼠心脏中，胰岛素刺激[14 C]亮氨酸产生14 CO2。在心脏灌注[14 C]亮氨酸，除了辛酸的灌注液不影响游离亮氨酸的组织浓度，也没有标记的亮氨酸池。辛酸刺激半横膈膜从亮氨酸产生14 CO2，半横膈膜预先装载有[14 C]亮氨酸，表明刺激亮氨酸氧化超过亮氨酸运输到肌细胞中。丙酮酸氧化和支链氨基酸氧化之间的明显反比关系表明，后者的调节可能发生在肌肉中支链α-酮酸的氧化脱羧。有人建议，在肌肉中的支链氨基酸catalysts的调节可以补充“丙氨酸循环”，并可能发挥作用，在稳态条件下的有限的葡萄糖的可用性（如禁食）或增加利用（如运动）。
Abstract Amino acid oxidation was studied in perfused hearts and incubated hemidiaphragms of rats fed ad libitum. Hearts were perfused with Krebs-Henseleit bicarbonate buffer containing glucose and 0.1 mm amino acids. The addition of 1 mm octanoate to the medium markedly stimulated 14CO2 production from [1-14C]leucine, isoleucine, and valine; inhibited 14CO2 production from [1-14C]alanine, pyruvate, and α-ketoglutarate, and did not affect 14CO2 production from [14C]histidine, threonine, glutamate, ornithine, and phenylalanine. Hemidiaphragms incubated with 1 mm hexanoate or 0.1 to 1.0 mm octanoate increased the oxidation of the branched chain amino acids by 80 to 200% and decreased 14CO2 production from alanine and pyruvate. Octanoate stimulated the oxidation of isoleucine by hemidiaphragms at isoleucine concentrations between 0.01 to 1.0 mm; when isoleucine exceeded 2 mm, octanoate became inhibitory. Octanoate stimulated the oxidation of the branched chain amino acids in the presence or absence of glucose and in the presence or absence of insulin from the medium, in diaphragms and hearts. Bovine serum albumin did not affect branched chain amino acid oxidation in the absence of added fatty acids; it inhibited the stimulatory effect of the latter. The inhibition was proportional to the albumin concentration. Palmitate and oleate (1 mm) added to albumin (15 mg per ml) stimulated branched chain amino acid oxidation by hemidiaphragms; the effect was smaller than that observed with equimolar octanoate and albumin. In hearts, no effect of 1 mm palmitate was observed. Butyrate (2 mm) did not affect branched chain amino acid oxidation by hemidiaphragms; 4 mm dl-β-OH butyrate and 4 mm acetate were inhibitory. In hearts and diaphragms, the omission of glucose from the incubation medium stimulated the oxidation of the branched chain amino acids. Pyruvate added to media containing glucose caused further inhibition of branched chain amino acid oxidation. Insulin stimulated 14CO2 production from [14C]leucine in hearts obtained from rats fasted for 48 hours and perfused without glucose. In hearts perfused with [14C]leucine, the addition of octanoate to the perfusate did not affect the tissue concentration of free leucine nor the labeling of the leucine pool. Octanoate stimulated 14CO2 production from leucine by hemidiaphragms which were preloaded with [14C]leucine, indicating stimulation of leucine oxidation beyond the transport of leucine into muscle cells. The apparent inverse relationship between the oxidation of pyruvate and that of the branched chain amino acids suggests that regulation of the latter may occur at the oxidative decarboxylation of the branched chain α-keto acids in muscles. It is suggested that regulation of branched chain amino acid catabolism in muscles may compliment the "alanine cycle," and may play a role in homeostasis under conditions of limited availability of glucose (e.g. fasting) or increased utilization (e.g. exercise).