Korzeniewski B, Harper M E, Brand M D
Department of Biochemistry, Cambridge University, UK.
Biochim Biophys Acta. 1995 May 10;1229(3):315-22. doi: 10.1016/0005-2728(95)00008-7.
A 'proportional activation' approach designed to deal with the influence of external effectors within biochemical systems is described. The proportional activation coefficient, which enables the quantitative determination of the relative stimulation of different parts of a system by a given effector, is defined. The proportional activation approach was used to calculate the relative activation of delta p-producing and delta p-consuming subsystems during stimulation of the respiration rate of cells by a variety of different effectors. Oxidative phosphorylation was stimulated by the addition of either lactate and pyruvate (10 mM and 1 mM) or vasopressin. The addition of lactate and pyruvate to suspensions of resting hepatocytes increased the respiration rate by about 50%. The delta p-consuming subsystem was stimulated about 60% as much as the delta p-producing subsystem. Quinolinic acid, commonly considered to be a specific inhibitor of gluconeogenesis, was found to block the delta p-producing oxidative subsystem as well as the delta p-consuming subsystem, indicating some nonspecific effects of this inhibitor. Addition of vasopressin to hepatocytes that were incubated in the presence of lactate and pyruvate resulted in an increase of the respiratory rate by up to 35%. The relative stimulation of the delta p-producing and delta p-consuming subsystems was essentially equal. Using the 'proportional activation approach' to analyse these and previously published data, it is shown that substrates (lactate/pyruvate and fatty acids), Ca(2+)-acting hormones (vasopressin and others) and calcium in muscles (heart muscle and skeletal muscle) activate both subsystems to a similar extent (it concerns especially Ca(2+)-dependent systems).
本文描述了一种旨在处理生化系统中外部效应物影响的“比例激活”方法。定义了比例激活系数，该系数能够定量测定给定效应物对系统不同部分的相对刺激程度。采用比例激活方法计算了多种不同效应物刺激细胞呼吸速率时，产生Δp和消耗Δp的子系统的相对激活情况。添加乳酸和丙酮酸（10 mM和1 mM）或血管加压素可刺激氧化磷酸化。向静止肝细胞悬液中添加乳酸和丙酮酸可使呼吸速率提高约50%。消耗Δp的子系统受到的刺激程度约为产生Δp的子系统的60%。通常被认为是糖异生特异性抑制剂的喹啉酸，被发现可阻断产生Δp的氧化子系统以及消耗Δp的子系统，表明该抑制剂存在一些非特异性作用。向在乳酸和丙酮酸存在下孵育的肝细胞中添加血管加压素，可使呼吸速率提高高达35%。产生Δp和消耗Δp的子系统的相对刺激程度基本相等。使用“比例激活方法”分析这些以及先前发表的数据表明，底物（乳酸/丙酮酸和脂肪酸）、Ca(2+)作用激素（血管加压素等）和肌肉（心肌和骨骼肌）中的钙对两个子系统的激活程度相似（尤其涉及Ca(2+)依赖系统）。
