FIGURE 10.

Respiratory studies of skeletal muscle mitochondria from iPLA₂γ^−/− and wild-type control mice fed the standard diet. Oxygen concentration and flux per volume (respiration) of isolated mitochondria from skeletal muscle was measured per mg of mitochondrial protein utilizing an Oroboros apparatus as described under “Experimental Procedures.” A and B, oxygen consumption in the presence of glutamate/malate (A) and palmitoylcarnitine/malate (B) are shown for wild-type (WT, solid bars) and iPLA₂γ^−/− (KO, open bars) mitochondria following additions of the indicated substrates and inhibitors. Oxygen consumption was significantly reduced following the addition of each substrate or inhibitor addition in the presence of either glutamate/malate (with the exception of oligomycin) or palmitoylcarnitine/malate in this study. C, significant increase in state 2/3 was observed for the KO utilizing glutamate/malate (p < 0.01), and a smaller but not significant increase was observed for palmitoylcarnitine/malate (p < 0.1). D, bar graphs showing significant reductions in state 3/4 metabolism utilizing glutamate/malate (p < 0.05) and palmitoylcarnitine/malate (p < 0.01). Male mice 9–11 months of age were utilized. n = 3–4/group. p < 0.05. E, ATP synthesis rate for muscle mitochondria. ATP synthesis of mitochondria was determined (mmol/min/mg mitochondrial protein) as described under “Experimental Procedures” for wild-type (WT) and iPLA₂γ^−/− (KO) samples from approximately 1-year-old male mice (n = 3–4 per group) on the standard diet. 2-Fold reductions in glutamate/malate (p < 0.01, complex I) and palmitoylcarnitine/malate (p < 0.05, complex I) ATP synthesis were observed in the KO. Data are presented as means ± S.E. Statistical significance was performed using the Student's t test, and significant differences are indicated by brackets and the associated p values. Abbreviations: AATA, antimycin A; TMPD, tetramethyl-p-phenylenediamine with ascorbate addition; palm-carn/malate, palmitoylcarnitine plus malate.