Metabolism of ethane and pentane to carbon dioxide by the rat

The pulmonary excretion rates of ethane and pentane have been used as indices of lipid peroxidation. This use assumes that exhalation of these hydrocarbons is directly related to their formation rate. This is true only if the elimination (metabolism plus nonpulmonary excretion) of ethane and pentane are constant in the presence of alterations in lipid peroxidation. However, the in vivo metabolic elimination profile for pentane is unknown and it has not been established with certainty that ethane is metabolized in vivo. Radiolabeled [14C]ethane and pentane were used to study the disposition of these hydrocarbons when injected into an enclosed chamber system containing a rat. The ethane and pentane concentrations in chamber air measured as 14C radioactivity were in general agreement with more selective measurements based on GC analysis. Pentane was cleared from chamber air at a much faster rate than ethane. Approximately 50 and 19.8% of the total radioactivity added to the chamber as [14C]pentane or [14c]ethane, respectively, was recovered as carbon dioxide at the end of 8 hr. The fraction of total radioactivity recovered in urine was 7.6 and 1.0% for the pentane and ethane experiments, respectively. These results indicate unequivocally that both ethane and pentane are metabolized in the intact rat.