Metabolic flux ratios assessed in working control (C) and mdx mouse heart perfused with 13C-labeled substrates. Data are given as means ± standard errors (indicated in parentheses); n = 4-8 in each group. Reactions are shown in the part of the cell in which they take place. (a) Flux ratios. (i) Flux ratios reflecting the contribution of exogenous fatty acids (oleate) and carbohydrates (CHOs: lactate, pyruvate and glucose) to acetyl-CoA formation (energy) and oxaloacetate (OAA; anaplerosis) via oleate β-oxidation (OLE), pyruvate decarboxylation (PDC) and carboxyation (PC), respectively, and expressed relative to citrate synthesis (CS). (ii) Flux ratios reflecting the contribution of individual CHOs - as indicated by the individual arrows - to pyruvate formation, expressed in percentage of total. (b) Glycolytic rate, which reflects the production of lactate and pyruvate, in μmol × min-1. (c) Tissue concentration of Krebs cycle intermediates, in μmol × g wet weight-1. (d) Tissue aconitase activity, in μmol × min-1 × mg protein-1. *p < 0.05, #p < 0.001 for mdx versus control mouse hearts. Adapted from Khairallah et al. .