Effects of guanidine derivatives on mitochondrial function. 3. The mechanism of phenethylbiguanide accumulation and its relationship to in vitro respiratory inhibition.
Effects of guanidine derivatives on mitochondrial function. 3. The mechanism of phenethylbiguanide accumulation and its relationship to in vitro respiratory inhibition.
复制标题
胍衍生物对线粒体功能的影响。
DOI：
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发表时间：
1971
影响因子：
4.8
通讯作者：
F. Davidoff
中科院分区：
文献类型：
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作者：
F. Davidoff
摘要 为深入了解胍衍生物体外抑制线粒体呼吸的机制，研究了不同代谢条件下豚鼠心脏线粒体中氚化苯乙基双胍的积累情况，并与呼吸抑制程度进行了比较。在低双胍浓度下，吸收速率缓慢，并且对培养基中的 pH 变化敏感；双胍的吸收程度与呼吸抑制程度相关，在最佳条件下，可达到约 100:1 的浓度梯度。在双胍浓度的 105 倍范围内，摄取率并未提供饱和的证据。在控制条件下，使用二甲基恶唑烷二酮分布技术测量培养基和基质空间之间的跨膜 pH 梯度，证明线粒体内 pH 值比培养基低约 0.6 个 pH 单位；线粒体内 pH 值不受双胍摄取抑制量的影响。增加单价和二价阳离子的浓度会逐渐提高线粒体内的 pH 值并减少双胍的摄取，低 K+ 浓度加上缬氨霉素的量太小而不会影响呼吸频率或控制。少量的长链游离脂肪酸引起双胍的流出，而不改变线粒体内的 pH 值或能量耦合。对电子传输抑制剂和解偶联剂的研究表明，需要能量来维持双胍的梯度吸收，尽管所需的能量很小。该数据不允许明确的解释，但似乎与双胍吸收的非离子扩散机制更一致，最终分布由跨膜pH梯度决定，而不是根据跨膜电位的分布。
Abstract To gain insight into the mechanism of in vitro mitochondrial respiratory inhibition by guanidine derivatives, the accumulation of tritiated phenethylbiguanide by guinea pig heart mitochondria was studied under various metabolic conditions and compared with the degree of respiratory inhibition. The rate of uptake was slow at low biguanide concentrations and was sensitive to pH changes in the medium; the extent of biguanide uptake correlated with the degree of respiratory inhibition, and under optimal conditions a concentration gradient of about 100:1 was achieved. Uptake rate did not give evidence of saturation over a 105-fold range of biguanide concentrations. Measurement of the transmembrane pH gradient between medium and matrix space under control conditions, using the technique of dimethyloxazolidinedione distribution, demonstrated the intramitochondrial pH to be about 0.6 pH units lower than that of the medium; intramitochondrial pH was not affected by uptake of inhibitory amounts of biguanide. Increasing concentrations of monovalent and divalent cation progressively raised intramitochondrial pH and diminished biguanide uptake, as did low K+ concentration plus valinomycin in amounts too small to affect respiratory rate or control. Small amounts of long chain free fatty acids caused an efflux of biguanide without altering either intramitochondrial pH or energy coupling. Studies with electron transport inhibitors and uncouplers indicated that energy was required to maintain biguanide uptake against a gradient, although the amount of energy needed was small. The data do not permit an unambiguous interpretation, but appear to be more consistent with a nonionic diffusion mechanism of biguanide uptake, with final distribution determined by the transmembrane pH gradient, than with distribution according to a transmembrane electrical potential.