Panchal A R, Comte B, Huang H, Kerwin T, Darvish A, des Rosiers C, Brunengraber H, Stanley W C
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA.
Am J Physiol Heart Circ Physiol. 2000 Nov;279(5):H2390-8. doi: 10.1152/ajpheart.2000.279.5.H2390.
The goal of this study was to measure flux through pyruvate carboxylation and decarboxylation in the heart in vivo. These rates were measured in the anterior wall of normal anesthetized swine hearts by infusing [U-(13)C(3)]lactate and/or [U-(13)C(3)] pyruvate into the left anterior descending (LAD) coronary artery. After 1 h, the tissue was freeze-clamped and analyzed by gas chromatography-mass spectrometry for the mass isotopomer distribution of citrate and its oxaloacetate moiety. LAD blood pyruvate and lactate enrichments and concentrations were constant after 15 min of infusion. Under near-normal physiological concentrations of lactate and pyruvate, pyruvate carboxylation and decarboxylation accounted for 4.7 +/- 0.3 and 41.5 +/- 2.0% of citrate formation, respectively. Similar relative fluxes were found when arterial pyruvate was raised from 0.2 to 1.1 mM. Addition of 1 mM octanoate to 1 mM pyruvate inhibited pyruvate decarboxylation by 93% without affecting carboxylation. The absence of M1 and M2 pyruvate demonstrated net irreversible pyruvate carboxylation. Under our experimental conditions we found that pyruvate carboxylation in the in vivo heart accounts for at least 3-6% of the citric acid cycle flux despite considerable variation in the flux through pyruvate decarboxylation.
本研究的目的是测量活体心脏中丙酮酸羧化和脱羧的通量。通过向左前降支（LAD）冠状动脉输注[U-(13)C(3)]乳酸和/或[U-(13)C(3)]丙酮酸，在正常麻醉猪心脏的前壁测量这些速率。1小时后，将组织冷冻钳夹，并通过气相色谱-质谱法分析柠檬酸及其草酰乙酸部分的质量同位素异构体分布。输注15分钟后，LAD血丙酮酸和乳酸的富集度及浓度保持恒定。在接近正常生理浓度的乳酸和丙酮酸条件下，丙酮酸羧化和脱羧分别占柠檬酸生成的4.7±0.3%和41.5±2.0%。当动脉丙酮酸从0.2 mM升高到1.1 mM时，发现了相似的相对通量。向1 mM丙酮酸中添加1 mM辛酸可抑制丙酮酸脱羧93%，而不影响羧化。未检测到M1和M2丙酮酸，表明丙酮酸羧化是净不可逆的。在我们的实验条件下，我们发现尽管丙酮酸脱羧通量存在相当大的变化，但活体心脏中的丙酮酸羧化至少占柠檬酸循环通量的3 - 6%。
