Costa L E, Méndez G, Boveris A
Instituto de Investigaciones Cardiológicas, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Am J Physiol. 1997 Sep;273(3 Pt 1):C852-8. doi: 10.1152/ajpcell.1997.273.3.C852.
Respiration and oxidative phosphorylation were investigated in tightly coupled mitochondria isolated from liver and heart of rats submitted to a simulated altitude of 4,400 m for 14-15 mo and their corresponding controls at sea level. High-resolution respirometry was utilized to determine the apparent Michaelis-Menten constant for ADP and O2 (K(m)-ADP and K(m)-O2, respectively), the latter under active and resting states of mitochondrial respiration. The K(m)-O2 in mitochondria isolated from normoxic rats was higher for active (state 3) than for resting (state 4) respiration; the values decreased from 1.5 and 1.7 to 0.25 and 0.30 microM in heart and liver mitochondria, respectively. The K(m)-O2 values found in the active state suggest a role for the normally occurring intracellular PO2 range reported in the literature in the regulation of cellular respiration. No changes were found in the ADP or O2 dependence of respiration in the mitochondria isolated from long-term acclimatized rats compared with their controls, indicating that the intrinsic properties and the efficiency of mitochondria do not change as a consequence of adaptation to hypoxia.
对从海拔4400米模拟环境中饲养14 - 15个月的大鼠肝脏和心脏分离出的紧密偶联线粒体及其海平面相应对照的线粒体进行了呼吸作用和氧化磷酸化研究。利用高分辨率呼吸测定法测定了ADP和O₂的表观米氏常数（分别为K(m)-ADP和K(m)-O₂），后者是在线粒体呼吸的活跃和静止状态下测定的。从常氧大鼠分离出的线粒体中，活跃呼吸（状态3）的K(m)-O₂高于静止呼吸（状态4）；心脏和肝脏线粒体中的该值分别从1.5和1.7微摩尔降至0.25和0.30微摩尔。活跃状态下的K(m)-O₂值表明，文献中报道的正常细胞内PO₂范围在细胞呼吸调节中起作用。与对照相比，从长期适应环境的大鼠分离出的线粒体中，呼吸作用对ADP或O₂的依赖性没有变化，这表明线粒体的内在特性和效率不会因适应低氧而改变。
