Studies on respiration and glycolysis in transplanted hepatic tumors of the rat.
Studies on respiration and glycolysis in transplanted hepatic tumors of the rat.
复制标题
大鼠移植性肝肿瘤呼吸和糖酵解的研究。
作者：
C. Lo;V. Cristofalo;H. Morris;S. Weinhouse
总结在一系列生长速率和分化程度广泛的大鼠肝癌中继续进行糖酵解和呼吸相互关系的研究，在28°C下，在存在果糖-1，6-二磷酸（FDP）、2-脱氧葡萄糖（2-DG）和外源性己糖激酶的情况下孵育这些组织的完整强化匀浆;测量呼吸、乳酸盐形成和2-DG摄取。该模型系统的初步研究表明，摄取2-DG是ATP形成的有效措施。假设每摩尔由FDP形成的乳酸盐通过磷酸甘油酸激酶和丙酮酸激酶产生2摩尔ATP，糖酵解磷酸化估计为乳酸盐的两倍，呼吸磷酸化计算为总ATP和糖酵解ATP形成之间的差异。在没有外源性底物的情况下，高分化肿瘤的匀浆呼吸高，而低分化肿瘤的匀浆呼吸低。在两种肿瘤类型中，呼吸与ATP形成相结合，产生1至2的P/O比。此外，FDP肝匀浆导致中度乳酸和糖酵解ATP的形成，后者主要是在呼吸磷酸化的代价。在分化良好的肿瘤组织匀浆中，乳酸形成和糖酵解磷酸化较低，呼吸和呼吸磷酸化均未降低。相比之下，低分化肝癌的匀浆表现出较高的乳酸盐形成，虽然呼吸增加了一定程度的FDP添加，基本上所有的ATP通过糖酵解形成。因此，在该系统中，糖酵解的转磷酸化酶是糖酵解控制的主要位点，可能是通过与呼吸ADP受体竞争可用的ADP。这种竞争的进一步证据是通过混合上清液和颗粒级分获得的。用来自高呼吸、高分化肿瘤的颗粒替换来自低呼吸、低分化肿瘤的颗粒，导致明显的巴斯德效应;呼吸增加，呼吸ATP产生增加，而糖酵解显着减少。然而，当用低呼吸肿瘤的颗粒代替高呼吸肿瘤的颗粒时，呼吸和呼吸磷酸化减少，糖酵解显著增加。这些发现为多年前约翰逊和Lynen提出的建议提供了证据，即巴斯德效应可能反映了在糖酵解和呼吸的转磷酸化位点对ADP和无机磷酸盐（P 1）的竞争。他们还表明，通常高度去分化肿瘤的特征是高有氧糖酵解，这可能部分是由于它们的低呼吸活性和高水平的糖酵解转磷酸酶。
Summary In a continuation of studies on glycolytic and respiratory interrelationships in a series of rat hepatomas ranging widely in growth rate and degree of differentiation, whole, fortified homogenates of these tissues were incubated at 28°C in the presence of fructose-1,6-diphosphate (FDP), 2-deoxyglucose (2-DG), and exogenous hexokinase; respiration, lactate formation, and uptake of 2-DG were measured. Preliminary studies with this model system established that uptake of 2-DG was a valid measure of ATP formation. On the assumption that each mole of lactate formed from FDP leads to production of 2 moles of ATP via phosphoglycerate kinase and pyruvate kinase, glycolytic phosphorylation was estimated as twice that of lactate, and respiratory phosphorylation was calculated as the difference between total ATP and glycolytic ATP formation. Without exogenous substrate, respiration was high in homogenates of well-differentiated tumors, and low in those of poorly differentiated tumors. In both tumor types respiration was coupled with ATP formation, yielding P/O ratios of 1 to 2. Addition of FDP to liver homogenates resulted in moderate lactate and glycolytic ATP formation, the latter being formed largely at the expense of respiratory phosphorylation. In homogenates of well-differentiated tumors, lactate formation and glycolytic phosphorylation were low, and neither respiration nor respiratory phosphorylation was decreased. In contrast, homogenates of the poorly differentiated hepatomas exhibited high lactate formation, and though respiration was increased somewhat by FDP addition, essentially all of the ATP was formed via glycolysis. It thus appears that, in this system, transphosphorylating enzymes of glycolysis are a major site of glycolytic control, presumably through competition with the respiratory ADP acceptors for the available ADP. Further evidence for such competition was obtained by intermixing the supernatant and particulate fractions. Replacement of particles from a low-respiring, poorly differentiated tumor by particles from a high-respiring, well-differentiated tumor resulted in a pronounced Pasteur effect; respiration was increased, together with respiratory ATP production, while glycolysis was markedly decreased. However, when particles of a high-respiring tumor were replaced with particles of a low-respiring tumor, respiration and respiratory phosphorylation were decreased and glycolysis was markedly increased. These findings provide evidence for the suggestion offered many years ago by Johnson and by Lynen that the Pasteur effect may reflect competition for ADP and inorganic phosphate (P 1 ) at the transphosphorylating sites of glycolysis and respiration. They also suggest that the high aerobic glycolysis which is, in general, characteristic of highly dedifferentiated tumors may be, in part, a resultant of their low respiratory activity and high levels of glycolytic transphosphorylating enzymes.