A Highly Sensitive Gas Chromatographic Method Does not Detect Exhalation of Volatile Hydrocarbons from Isolated Ventilated Lungs under Massive Peroxidative Stress

Abstract

Lung lipid peroxidation is thought to be a basic pathophysiological phenomenon responsible for pulmonary damage in different types of oxidant attack. Measurement of volatile hydrocarbons, especially ethane and pentane, produced during peroxidative degradation of polyunsaturated fatty acids and exhaled into an animal housing chamber, has attracted increasing interest for the monitoring of in vivo lipid peroxidation. However, this approach cannot distinguish between pulmonary exhalation of hydrocarbons generated in different organs or even the intestinum and pulmonary generation of these lipid peroxidation markers. In the present study we developed a respiration and hydrocarbon trapping system for isolated, ventilated, and perfused lungs that avoided re-breathing and allowed complete sampling and gas chromatographic separation and quantification of exhaled alkanes and alkenes (C₁-C₅) in the absence of background levels. Using an “artificial lung,” the recoveries of exogenously administered hydrocarbons ranged between 80 and 95% with good reproducibility (SD between 1.7 and 9.6%). The detection limit of the system was ñ3 fmol of each alkane or alkene/g wet lung weight- min. However, neither under basal conditions nor during massive peroxidative stress by the application of high doses of H₂O₂, FeCl₃/ascorbate, paraquat, or ozone was any material with a retention time similar to that of hydrocarbons exhaled from isolated rabbit lungs. We conclude that under the experimental conditions employed, there is only insignificant generation of hydrocarbons in intact lungs.