Saddik M, Lopaschuk G D
Department of Pediatrics, University of Alberta, Edmonton, Canada.
J Biol Chem. 1991 May 5;266(13):8162-70.
The objective of this study was to determine the contribution of myocardial triglycerides to overall ATP production in isolated working rat hearts. Endogenous lipid pools were initially prelabeled (pulsed) by perfusing hearts for 60 min with Krebs-Henseleit buffer containing 1.2 mM [1-14C]palmitate. During a subsequent 60-min period (chase), hearts were perfused with either no fat, low fat (0.4 mM [9,10-3H] palmitate), or high fat (1.2 mM [9,10-3H]palmitate). All buffers contained 11 mM glucose. During the "chase," 14CO2 production (a measure of endogenous fatty acid oxidation) and 3H2O production (a measure of exogenous fatty acid oxidation) were determined. Oxidative rates of endogenous fatty acids during the chase were 279 +/- 50, 88 +/- 14, and 88 +/- 8 nmol of [14C]palmitate oxidized per g dry weight.min in the no fat, low fat, and high fat groups, respectively, compared to exogenous palmitate oxidation rates of 0, 361 +/- 68, and 633 +/- 60 nmol of [3H]palmitate/g dry weight.min, in the no fat, low fat, and high fat groups, respectively. Endogenous [14C]palmitate oxidation rates were matched by loss of [14C]palmitate from endogenous myocardial triglycerides. Overall triglyceride content decreased during the no fat and low fat chase perfusion but did not change during the high fat chase. Loss of triglyceride [14C]palmitate during the high fat chase was matched by incorporation of exogenous [3H]palmitate in triglycerides. In a second series of perfusions, three groups of hearts were perfused under similar conditions, except that unlabeled palmitate was used during the "pulse" and that 11 mM [2-3H/U-14C]glucose and unlabeled palmitate was present during the chase. During the chase, both glycolysis (3H2O production) and glucose oxidation (14CO2 production) rates were measured. Rates of glucose oxidation were inversely related to the fatty acid concentration in the perfusate (1257 +/- 158, 366 +/- 40, and 124 +/- 26 nmol of glucose oxidized per min.g dry weight in the no fat, low fat, and high fat groups, respectively), while rates of glycolysis were not significantly different between these groups. Calculation of overall ATP production from both oxidative and glycolytic sources determined that even in the presence of high concentrations of fatty acids, myocardial triglyceride turnover can provide over 11% of steady state ATP production in the aerobically perfused heart. In the absence of fatty acids, myocardial triglyceride fatty acids can become the major energy substrate of the heart.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究的目的是确定心肌甘油三酯对离体工作大鼠心脏总ATP生成的贡献。通过用含1.2 mM [1-14C]棕榈酸的 Krebs-Henseleit 缓冲液灌注心脏60分钟，对内源性脂质池进行初始预标记（脉冲标记）。在随后的60分钟期间（追踪期），心脏分别用无脂肪、低脂（0.4 mM [9,10-3H]棕榈酸）或高脂（1.2 mM [9,10-3H]棕榈酸）灌注。所有缓冲液均含有11 mM葡萄糖。在“追踪期”，测定14CO2生成量（内源性脂肪酸氧化的指标）和3H2O生成量（外源性脂肪酸氧化的指标）。追踪期内，无脂肪、低脂和高脂组内源性脂肪酸的氧化速率分别为每克干重·分钟氧化279±50、88±14和88±8 nmol的[14C]棕榈酸，而无脂肪、低脂和高脂组外源性棕榈酸的氧化速率分别为0、361±68和633±60 nmol的[3H]棕榈酸/克干重·分钟。内源性[14C]棕榈酸的氧化速率与内源性心肌甘油三酯中[14C]棕榈酸的损失相匹配。在无脂肪和低脂追踪灌注期间，总甘油三酯含量下降，但在高脂追踪期间没有变化。高脂追踪期间甘油三酯[14C]棕榈酸的损失与外源性[3H]棕榈酸掺入甘油三酯相匹配。在第二系列灌注中，三组心脏在相似条件下灌注，不同之处在于“脉冲”期间使用未标记的棕榈酸，追踪期间存在11 mM [2-3H/U-14C]葡萄糖和未标记的棕榈酸。在追踪期间，测量糖酵解（3H2O生成）和葡萄糖氧化（14CO2生成）速率。葡萄糖氧化速率与灌注液中脂肪酸浓度呈负相关（无脂肪、低脂和高脂组分别为每分钟·克干重氧化1257±158、366±40和124±26 nmol葡萄糖），而这些组之间的糖酵解速率没有显著差异。从氧化和糖酵解来源计算总ATP生成量确定，即使在存在高浓度脂肪酸的情况下，心肌甘油三酯周转仍可在有氧灌注的心脏中提供超过11%的稳态ATP生成。在没有脂肪酸的情况下，心肌甘油三酯脂肪酸可成为心脏的主要能量底物。（摘要截断于400字）
