Expiration of ethane in rats under variously elevated inspiratory O2-concentrations

Expired ethane is regarded as a noninvasive indicator of lipid peroxidation. As a model of oxidative stress we have investigated in male Wistar rats (body wt. 309 +/- 15 g) the effects of various levels of elevated inspiratory oxygen concentrations on the expiration rate of ethane. After 4 days under 21 vol% O2 (basic condition) the rats were exposed for 6 or 5 days to 40, 60 or 80 vol% O2 over 8 or 23 h/day. The variously O2-enriched air was conducted through the cages and expired ethane adsorbed onto charcoal was thermo-desorbed and measured by gas chromatography. Basic ethane expiration was 3.1 +/- 0.8 pmol/100 g body wt. per min. At 40 vol% O2 over 8 or 23 h/day no increase or a maximum average 47% increase (P < 0.01) in ethane expiration occurred on day 4; 60 vol% O2 over 8 or 23 h/day led to a corresponding increase of 56 or 87% (P < 0.05 or P < 0.01) on day 3; 80 vol% O2 over 8 or 23 h/day led to a corresponding increase of 81 or 66% (P < 0.01) on days 3 or 2. Our results indicate that with up to 60 vol% O2 a temporary increase in lipid peroxidation occurs in a dose dependent manner. However, at 80 vol% O2 no further increase in the maximum ethane expiration occurred. The latter finding and the finding of only transient increase in ethane expiration in probably due to antioxidative counteraction.