Dependence of oxidation and phosphorylation rates on ADP concentration in liver and muscle mitochondria.

<p>Oxidation and phosphorylation rates were recorded simultaneously in liver (n = 4) and muscle (n = 5) mitochondria oxidizing glutamate+malate+succinate as substrates. True steady state of oxidation and phosphorylation rates were obtained using coupled enzymatic system composed of Glucose (5 mM) - Hexokinase (2.5 U.ml⁻¹, Sigma-Aldrich, H4502) - Glucose-6-phosphotate dehydrogenase (2.5 U.ml⁻¹, Sigma-Aldrich, G6378) - NADP⁺ (1.6 mM). Data presented in panels A and B correspond to absolute oxidation and phosphorylation rates, respectively. Maximal oxidation and phosphorylation rates obtained for muscle and liver mitochondria were 408.0±42.5 vs. 85.2±5.5 nmolO₂.min⁻¹.mg⁻¹ and 1672.8±134.1 vs. 361.3±33.41 nmolATP.min⁻¹.mg⁻¹, respectively. Panels C and D show normalized oxidation and phosphorylation rates, respectively. Data were fitted using the Michaelis-Menten equation presented in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020709#s2" target="_blank">materials and methods</a> section. Data are presented as mean ± SD. Differences were tested using an unpaired bilateral student's t-test. ** p<0.01 between liver and muscle, # p<0.01 vs. KmVox.