Breath ethane as a marker of reactive oxygen species during manipulation of diet and oxygen tension in rats

Breath ethane, O₂consumption, and CO₂ production were analyzed in 24-mo-old female Fischer 344 rats that had been fed continuously ad libitum (AL) or restricted 30% of AL level (DR) diets since 6 wk of age. Rats were placed in a glass chamber that was first flushed with air, then with a gas mixture containing 12% O₂. After equilibration, a sample of the outflow was collected in gas sampling bags for subsequent analyses of ethane and CO₂. The O₂ and CO₂ levels were also directly monitored in the outflow of the chamber. O₂ consumption and CO₂ production increased for DR rats. Hypoxia decreased O₂consumption and CO₂ production for the AL-fed and DR rats. These changes reflect changes in metabolic rate due to diet and $P{O}_2$ . A significant decrease in ethane generation was found in DR rats compared with AL-fed rats. Under normoxic conditions, breath ethane decreased from 2.20 to 1.61 pmol ethane/ml CO₂. During hypoxia the levels of ethane generation increased, resulting in a DR-associated decrease in ethane from 2.60 to 1.90 pmol ethane/ml CO₂. These results support the hypothesis that DR reduces the level of oxidative stress.