Unusual peaks of oxygen consumption under special alimentary conditions

Oxygen consumption (VO2), carbon dioxide production (VCO2), the resulting respiratory quotient (RQ), and motor activity were recorded simultaneously by an on-line computer every ten seconds during 16-20 hours in two decerebrate male rats. Being aphagic and adipsic the rats were fed twice daily by gastric intubation with a mixture of powdered milk plus sugar or plus sunflower oil (approx. 300 KJ daily) in 10-20 ml tap water. In all seven tests performed on these rats the recordings presented very steep reductions of RQ due every time to steep increases in VO2 without increases in VCO2. Mean number of VO2 peaks in all experiments was 12.4 +/- 1.8 (SE) with mean duration of 21.3 +/- 2.8 min. Two normal male rats were fed the same diet and on the same schedule: they presented similar VO2 peaks in 8 out of 12 experiments. Mean number was 8.7 +/- 1.0 with mean duration of 13.6 +/- 2.2 min. The VO2 peak periods never occurred in rats fed ad libitum. In the two normal rats oil ingestion produced more effect than sugar. It is suggested that the phenomenon could be due to a metabolic imbalance possibly of hepatic origin, more evident in decerebrate rats. VO2 peaks could be produced by enhanced ketogenesis, gluconeogenesis and/or extra-mitochondrial (peroxisomal, microsomal) oxidation.