Sequences of protocol applied to measure resynthesis of total ATP and glycogen contents, and unidirectional flux of mitochondrial ATP synthesis. All the processes post-feeding occurred in vivo in integrated physiological conditions. The ex vivo step is the only way to estimate the mitochondrial contribution to ATP synthesis. The ex vivo step performed rapidly at each time post force-feeding reflects the in vivo situation. The total ATP and glycogen contents in controls fed ad libitum were 2.70 ± 0.30 and 74.97 ± 11.17 μmol/g liver wet weight, respectively. In 48-hr fasted controls, total ATP and glycogen contents were 0.95 ± 0.29 and 0.80 ± 0.10 μmol/g liver ww, respectively. In the force-feeding step, the bolus (expressed per g body weight) was isocaloric (7.28 kcal): 18.2 mg glucose or 14 mg glucose + 1.9 mg butyrate.