UPTAKE AND RETENTION OF HEXAKIS (2-METHOXYISOBUTYL ISONITRILE) TECHNETIUM(I) IN CULTURED CHICK MYOCARDIAL-CELLS - MITOCHONDRIAL AND PLASMA-MEMBRANE POTENTIAL DEPENDENCE
UPTAKE AND RETENTION OF HEXAKIS (2-METHOXYISOBUTYL ISONITRILE) TECHNETIUM(I) IN CULTURED CHICK MYOCARDIAL-CELLS - MITOCHONDRIAL AND PLASMA-MEMBRANE POTENTIAL DEPENDENCE
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DOI：
10.1161/01.cir.82.5.1826
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发表时间：
1990-11-01
期刊：
影响因子：
37.8
通讯作者：
CHIU, ML
中科院分区：
文献类型：
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作者：
PIWNICAWORMS, D;KRONAUGE, JF;CHIU, ML
锝-99m心肌灌注显像剂六（2-甲氧基异丁基异腈）锝（I）（Tc-MIBI）的基本肌细胞摄取和保留机制尚未解决。由于Tc-MIBI的亲脂性阳离子性质，其可响应于跨膜电位而跨生物膜分布。为了验证这一假设，在已知改变线粒体和质膜电位的条件下，在培养的鸡胚心室肌细胞中测定Tc-MIBI的净摄取和保留。在130 mM细胞外K（Ko）20 mM细胞外Cl缓冲液中质膜电位的等容去极化将Tc-MIBI的净积累从171 ± 100 μ g/ml降低到171 ± 100 μ g/ml。16（对照）至29 .+-。3.3 fmol细胞内Tc-MIBI/mg蛋白质. nM细胞外Tc-MIBI。在30 mM Ko缓冲液中去极化的细胞中Tc-MIBI的单向流入也减少;静息质膜电位为-87 ± 1。使用正常Ko/高Ko Tc-MIBI流入比从Goldman通量方程计算6 mV。向在130 mM Ko缓冲液中孵育的细胞中添加钾离子载体缬氨霉素以额外降低线粒体膜电位，进一步将Tc-MIBI的净摄取降低至与在非活冻融制剂中发现的水平相当的水平（[Tc-MIBI]i/[Tc-MIBI]o = 1）。通过用质子载体2，4-二硝基苯酚和羰基氰化物间氯苯腙（CCCP）使线粒体（和部分质膜）电位去极化，Tc-MIBI从181 ± 1迅速耗尽。16（对照）至16 .+-。2.6和31 .+-. 4.2 fmol/mg蛋白质。nMo，动力学与细胞ATP含量的损失无关。CCCP单独抑制90 . ±.净积累的3%或66 .+-。3%的Tc-MIBI以浓度依赖性方式单向内流。通过用K+/H+离子载体尼日利亚菌素或ATP合成酶抑制剂寡霉素使线粒体膜电位超极化，Tc-MIBI的净摄取和保留增加60 ± 10%。9%和375 . ±.分别为20%。咖啡因，以及呼吸链电子传递抑制剂鱼藤酮，没有显着改变净细胞摄取（p > 0.2）。这些数据表明，Tc-MIBI的基本肌细胞摄取机制涉及跨质膜和线粒体膜的被动分布，并且在平衡时，Tc-MIBI通过大的负跨膜电位被隔离在线粒体内。
The fundamental myocellular uptake and retention mechanisms of hexakis (2-methoxyisobutylisonitrile) technetium(I) (Tc-MIBI), a technetium-99m-based myocardial perfusion imaging agent, are unresolved. Because of the lipophilic cationic nature of Tc-MIBI, it may be distributed across biological membranes in response to transmembrane potential. To test this hypothesis, net uptake and retention of Tc-MIBI in cultured chick embryo ventricular myocytes were determined under conditions known to alter mitochondrial and plasma membrane potentials. Isovolumic depolarization of plasma membrane potentials in 130 mM extracellular K (Ko) 20 mM extracellular Cl buffer reduced net accumulation of Tc-MIBI from 171 .+-. 16 (control) to 29 .+-. 3.3 fmol intracellular Tc-MIBI/mg protein .cntdot. nM extracellular Tc-MIBI. Unidirectional influx of Tc-MIBI in cells depolarized in 30 mM Ko buffer was also reduced; a resting plasma membrane potential of -87 .+-. 6 mV was calculated from the Goldman flux equation using normal Ko/high Ko Tc-MIBI influx ratios. Addition of the potassium ionophore valinomycin to cells incubated in 130 mM Ko buffer to additionally depolarize mitochondrial membrane potentials further reduced net uptake of Tc-MIBI to levels comparable to that found in nonviable freeze-thawed preparations ([Tc-MIBI]i/[Tc-MIBI]o = 1). By depolarizing mitochondrial (and in part plasma membrane) potentials with the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone (CCCP) Tc-MIBI was rapidly depleted from 181 .+-. 16 (control) to 16 .+-. 2.6 and 31 .+-. 4.2 fmol/mg protein .cntdot. nMo, respectively, with kinetics that did not correlate with loss of cellular ATP content. CCCP alone inhibited 90 .+-. 3% of net accumulation or 66 .+-. 3% of unidirectional influx of Tc-MIBI in a concentration-dependent manner. By hyperpolarizing mitochondrial membrane potentials with the K+/H+ ionophore nigericin or the ATP synthase inhibitor oligomycin, net uptake and retention of Tc-MIBI were increased by 60 .+-. 9% and 375 .+-. 20%, respectively. Caffeine, as well as the respiratory chain electron transport inhibitor rotenone, did not significantly alter net cell uptake (p > 0.2). These data indicate that the fundamental myocellular uptake mechanism of Tc-MIBI involves passive distribution across plasma and mitochondrial membranes and that at equilibrium Tc-MIBI is sequestered within mitochondria by the large negative transmembrane potentials.