Griffin J L, O'Donnell J M, White L T, Hajjar R J, Lewandowski E D
Departments of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Am J Physiol Cell Physiol. 2000 Dec;279(6):C1704-9. doi: 10.1152/ajpcell.2000.279.6.C1704.
This study examines the functional implications of postnatal changes in the expression of the mitochondrial transporter protein, 2-oxoglutarate-malate carrier (OMC). Online (13)C nuclear magnetic resonance ((13)C NMR) measurements of isotope kinetics in hearts from neonate (3-4 days) and adult rabbits provided tricarboxylic acid cycle flux rates and flux rates through OMC. Neonate and adult hearts oxidizing 2.5 mM [2,4-(13)C(2)]butyrate were subjected to either normal or high cytosolic redox state (2.5 mM lactate) conditions to evaluate the recruitment of malate-aspartate activity and the resulting OMC flux. During development from neonate (3-4 days) to adult, mitochondrial protein density in the heart increased from 19 +/- 3% to 31 +/- 2%, whereas OMC expression decreased by 65% per mitochondrial protein content (P < 0.05). Correspondingly, OMC flux was lower in adults hearts than in neonates by 73% (neonate = 7. 4 +/- 0.4, adult = 2.0 +/- 0.1 micromol/min per 100 mg mitochondrial protein; P < 0.05). Despite clear changes in OMC content and flux, the responsiveness of the malate-aspartate shuttle to increased cytosolic NADH was similar in both adults and neonates with an approximate threefold increase in OMC flux (in densitometric units/100 mg mitochondrial protein: neonate = 25.8 +/- 2.5, adult = 6.0 +/- 0.2; P < 0.05). The (13)C NMR data demonstrate that OMC activity is a principal component of the rate of labeling of glutamate.
本研究探讨了线粒体转运蛋白2-氧代戊二酸-苹果酸载体（OMC）表达的产后变化的功能影响。通过在线¹³C核磁共振（¹³C NMR）测量新生（3 - 4天）和成年兔心脏中的同位素动力学，得出三羧酸循环通量率和通过OMC的通量率。将氧化2.5 mM [2,4-(¹³C₂)]丁酸的新生和成年心脏置于正常或高细胞质氧化还原状态（2.5 mM乳酸）条件下，以评估苹果酸-天冬氨酸活性的募集以及由此产生的OMC通量。从新生（3 - 4天）发育到成年的过程中，心脏中的线粒体蛋白密度从19±3%增加到31±2%，而OMC表达相对于每个线粒体蛋白含量下降了65%（P < 0.05）。相应地，成年心脏中的OMC通量比新生心脏低73%（新生 = 7.4±0.4，成年 = 2.0±0.1微摩尔/分钟每100毫克线粒体蛋白；P < 0.05）。尽管OMC含量和通量有明显变化，但苹果酸-天冬氨酸穿梭对细胞质NADH增加的反应性在成年和新生心脏中相似，OMC通量增加约三倍（以光密度单位/100毫克线粒体蛋白计：新生 = 25.8±2.5，成年 = 6.0±0.2；P < 0.05）。¹³C NMR数据表明，OMC活性是谷氨酸标记速率的主要组成部分。
