Darnold J R, Vorbeck M L, Martin A P
Department of Pathology, University of Missouri School of Medicine, Columbia 65212.
Mech Ageing Dev. 1990 Apr 9;53(2):157-67. doi: 10.1016/0047-6374(90)90067-p.
The proposed study was undertaken to investigate the effect of aging on control of the oxidative phosphorylation pathway. Flux control coefficients for adenine nucleotide translocase and cytochrome c oxidase were determined using the procedure of Groen et al. [J. Biol. Chem., 257 (1982) 137-144]. Hepatic mitochondrial fractions from Fischer 344 rats were isolated from control (average age 6.5 months), and aged (average age 27.3 months) groups. No aging-related changes in the extent of control of respiration by the oxidase were obtained, however, differences were observed for the translocase. For the control group of animals, the greatest regulation occurred at 80-85% maximal respiratory rates, and declined at higher rates. For the aged group, a similar flux control coefficient was obtained at 80-85% respiration, but was maintained as respiration increased to maximal rates. It is proposed that changes in the flux control coefficients at maximal respiratory rates are associated with an aging-related decrease in translocase activity. Evaluation of translocase content revealed no significant differences between the two groups supporting the concept that the decreased activity was not due to decreased content. During the course of these experiments, it also became apparent that there was a significant aging-related decrease in the rate of succinate oxidation providing an adequate supply of ADP was present. No significant changes in respiratory rates, or RCR, were evident at suboptimal concentrations of ADP as reported previously from this laboratory [Vorbeck, M.L. et al., Arch. Biochem. Biophys., 214 (1982) 67-79]. Since similar decreases in respiration were obtained upon addition of an uncoupler, the aging-related changes in respiration are attributed to differences at the level of the electron transport system, including its associated reactions. The aging-related differences in respiratory rates, and extent of control of respiration, were both observed under conditions of maximal stimulation of respiration. This suggests an inability of mitochondria from aged animals to respond to the increased demands of oxidation. Basic to these differences may be the lipid-membrane associated changes seen during aging.
本研究旨在探讨衰老对氧化磷酸化途径调控的影响。采用Groen等人[《生物化学杂志》，257 (1982) 137 - 144]的方法测定腺嘌呤核苷酸转位酶和细胞色素c氧化酶的通量控制系数。从对照（平均年龄6.5个月）和老年（平均年龄27.3个月）组的Fischer 344大鼠中分离出肝脏线粒体部分。然而，未观察到氧化酶对呼吸控制程度的衰老相关变化，但转位酶存在差异。对于对照组动物，最大调节作用出现在最大呼吸速率的80 - 85%，且在更高速率时下降。对于老年组，在80 - 85%呼吸时获得类似的通量控制系数，但随着呼吸增加到最大速率时保持不变。据推测，最大呼吸速率时通量控制系数的变化与转位酶活性的衰老相关降低有关。转位酶含量评估显示两组之间无显著差异，支持活性降低并非由于含量降低的观点。在这些实验过程中，还明显发现，在有足够ADP供应的情况下，琥珀酸氧化速率存在显著的衰老相关降低。如本实验室先前报道[Vorbeck, M.L.等人，《生物化学与生物物理学档案》，214 (1982) 67 - 79]，在次优ADP浓度下，呼吸速率或呼吸控制率无明显变化。由于加入解偶联剂后呼吸也有类似降低，呼吸的衰老相关变化归因于电子传递系统水平的差异，包括其相关反应。呼吸速率和呼吸控制程度的衰老相关差异均在呼吸最大刺激条件下观察到。这表明老年动物的线粒体无法应对氧化需求的增加。这些差异的根本原因可能是衰老过程中脂质膜相关的变化。
