Respiration and ATP synthesis rates were measured in the same mitochondrial aliquots as described previously for bird muscle mitochondria (Teulier et al., 2010; Salin et al., 2010). Oxygen consumption was measured in a glass cell fitted with a Clark oxygen electrode (Rank Brothers Ltd, UK), at 38°C and calibrated with air-saturated respiratory buffer (120 mmol l−1 KCl, 5 mmol l−1 KH2PO4, 1 mmol l−1 EGTA, 2 mmol l−1 MgCl2, 2.5 mmol l−1 malate, 20 mmol l−1 glucose, 1.5 U ml−1 hexokinase, 0.3% BSA (w/v), and 3 mmol l−1 Hepes, pH 7.4 at 38°C). Muscle mitochondria (1 mg protein ml−1) were incubated in the respiratory buffer supplemented with 5 mmol l−1 pyruvate or 40 μmol l−1 palmitoyl-l-carnitine. Different steady states of phosphorylation were initiated by adding different amounts of ADP from 5 to 100 μmol l−1. After recording the phosphorylating respiration rate for 2 min, four 100 μl aliquots of mitochondrial suspension were withdrawn every 30 s and quenched in a perchloric acid solution (10% HClO4, 25 mmol l−1 EDTA). The denatured proteins were centrifuged at 15,000 g for 5 min and the resulting supernatant neutralized with a KOH solution (2 M KOH, 0.3 M Mops). Then, the ATP production was determined from the glucose-6-phosphate content of the samples, which was measured enzymatically by spectrophotometry according to Lang and Michal (Lang and Michal, 1974). Basal non-phosphorylating respiration rates were determined in the presence of 2 μg ml−1 oligomycin.