Mitochondrial transmembrane pH and electrical gradients: evaluation of their energy relationships with respiratory rate and adenosine 5'-triphosphate synthesis.
Mitochondrial transmembrane pH and electrical gradients: evaluation of their energy relationships with respiratory rate and adenosine 5'-triphosphate synthesis.
复制标题
线粒体跨膜 pH 值和电梯度：评估其能量与呼吸频率和 5-三磷酸腺苷合成的关系。
作者：
D. Wilson;N. Forman
将大鼠肝脏线粒体悬浮在离子介质中，平行测量呼吸频率、线粒体内体积和磷酸化状态[[ATP]/([ADP][PI])]，以及跨膜pH梯度(来自标记的弱酸和碱的分布)和电梯度(来自标记的脂溶离子的分布和在呋喃霉素存在下的K+的分布)。加入丙酸钠、醋酸盐或乳酸盐可使pH梯度降低。在丙酸的情况下，pH梯度从-0.94+/-0.10(对照)下降到-0.09+/-0.08单位(丙酸3 mM)，其他任何测量参数都没有变化。线粒体内体积的变化是通过改变[K+](+呋喃霉素)和稀释氯化胆碱来实现的。在70molM或8 mM K+(+valinmycin)存在的条件下，跨膜电位从对照条件下的-150 mV降至约-75 mV。[ATP]/([ADP][PI])的变化如下：当渗透压从300降至70molM时，加入8 mM K+(+呋喃霉素)或1.0×10(4)M-1时，[ATP]/([ADP][PI])从1.8×10(4)(对照组)降至3.9×10(2)M-1。这与添加K+时用于合成ATP的能量从14.1千卡/摩尔下降到11.9千卡/摩尔(从58.9千卡/摩尔下降到49.7千卡/摩尔)和在渗透压降低时降低到13.8千卡/摩尔(57.7千卡/摩尔)相对应。跨膜电位、pH梯度或总质子电化学梯度的变化与呼吸频率或[ATP]/([ADP][PI])之间没有直接的相关性。
Mitochondria from rat liver were suspended in ionic media, and parallel measurements were made of the respiratory rate, intramitochondrial volumes, and the phosphorylation state [[ATP]/([ADP][Pi])], as well as transmembrane pH gradients (from the distribution of labeled weak acids and bases) and electrical gradients (from the distribution of labeled lipid-soluble ions and of K+ in the presence of valinomycin). A decrease in the pH gradient was observed with additions of sodium propionate, acetate, or lactate. In the case of propionate, the pH gradient decreased from -0.94 +/- 0.10 (control) to -0.09 +/- 0.08 unit (with 3 mM propionate) without change in any of the other measured parameters. Variation of the intramitochondrial volumes was achieved by changing [K+] (+valinomycin) and by diluting the choline chloride media. The transmembrane electrical potential decreased from -150 mV under control conditions to approximately -75 mV in a 70 mosM medium or when 8 mM K+ (+valinomycin) was present. The changes in [ATP]/([ADP][Pi]) were as follows: from 1.8 X 10(4) (control) to 3.9 X 10(2) M-1 with 8 mM K+ (+valinomycin) or 1.0 X 10(4) M-1 when the osmolarity was decreased from 300 to 70 mosM. This corresponds to a decrease in the energy utilized for ATP synthesis from 14.1 to 11.9 kcal/mol (from 58.9 to 49.7 kJ/mol) with added K+ and to 13.8 kcal/mol (57.7 kJ/mol) with decreased osmolarity. No direct correlation was found between the changes in transmembrane electrical potential, pH gradient, or total proton electrochemical gradient and either the respiratory rate or [ATP]/([ADP][Pi]).