UNCOUPLING EFFECT OF THE GENERAL ANESTHETIC 2,6-DIISOPROPYLPHENOL IN ISOLATED RAT-LIVER MITOCHONDRIA
UNCOUPLING EFFECT OF THE GENERAL ANESTHETIC 2,6-DIISOPROPYLPHENOL IN ISOLATED RAT-LIVER MITOCHONDRIA
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DOI：
10.1016/0003-9861(91)90575-4
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发表时间：
1991-11-01
影响因子：
3.9
通讯作者：
SCUTARI, G
中科院分区：
文献类型：
--
作者：
BRANCA, D;ROBERTI, MS;SCUTARI, G
2，6-二异丙基苯酚是一种全身麻醉剂，以前曾报道过降低离体大鼠肝线粒体的跨膜电位，而不影响ATP产生速率。这种效应似乎与普遍接受的氧化磷酸化的化学渗透机制形成对比。在这项研究中，我们进一步研究了2，6-二异丙基苯酚对ATP的生产的影响，通过分离的线粒体，我们研究了其对线粒体内膜的渗透性质子的影响。为了阐明2，6-二异丙基苯酚对线粒体ATP生成的影响，测定了腺嘌呤核苷酸转运体和ATP合成酶的活性。所获得的结果表明，由2，6-二异丙基苯酚引起的跨膜电位的抑制降低了ATP合成酶的活性（如能量耦合的化学渗透模型中所预期的），但不是腺嘌呤核苷酸转运蛋白的活性。然而，ATP合成酶活性的降低，并没有导致在一个明显的抑制ATP生产的整体速度在分离的线粒体由于在这个过程中的腺嘌呤核苷酸转运的限速作用。此外，发现2，6-二异丙基苯酚增加线粒体内膜对质子的渗透性;随着孵育介质的pH值增加，这种效应变得更加显著，表明它涉及2，6-二异丙基苯酚的解离形式。这些观察结果表明，2，6-二异丙基苯酚影响氧化磷酸化作为一个温和的质子载体，其有效性是有限的苯酚解离在接近生理pH值的低分数。
2,6-Diisopropylphenol, a general anesthetic, was previously reported to reduce the transmembrane electrical potential in isolated rat liver mitochondria without affecting the rate of ATP production. This effect appeared to contrast with the generally accepted chemiosmotic mechanism for oxidative phosphorylation. In this study we further examined the influence of 2,6-diisopropylphenol on the production of ATP by isolated mitochondria and we studied its effect on the permeability of the inner mitochondrial membrane to protons. In order to clarify the effects of 2,6-diisopropylphenol on mitochondrial ATP production the activities of the adenine nucleotide translocator and the ATP synthetase were evaluated. The results obtained indicate that the depression of the transmembrane electrical potential elicited by 2,6-diisopropylphenol decreased the activity of the ATP synthetase (as expected in the chemiosmotic model for energy coupling), but not that of the adenine nucleotide translocator. The decrease of the ATP synthetase activity, however, did not result in an apparent inhibition of the overall rate of ATP production in isolated mitochondria due to the rate-limiting effect of the adenine nucleotide translocator in this process. Moreover 2,6-diisopropylphenol was found to increase the permeability to protons of the inner mitochondrial membrane; this effect became more marked as the pH of the incubation medium was increased, demonstrating that it involved the dissociated form of 2,6-diisopropylphenol. These observations suggested that 2,6-diisopropylphenol affected oxidative phosphorylation by acting as a mild protonophore and that its effectiveness was limited by the low fraction of phenol dissociated at near-physiological pH.