The composition of alkanes in exhaled air of rats as a result of lipid peroxidation in vivo. Effects of dietary fatty acids, vitamin E and selenium.

Alkane production in exhaled air of rats has been studied as an index of lipid peroxidation in vivo in these animals. The effect of feeding essential fatty acid-deficient rats varying levels of n-4, n-6 and n-7 polyunsaturated fatty acids for various periods of time has been studied with regard to the composition of the alkanes produced as well as the fatty acid composition of liver phospholipids and liver and adipose tissue triacylglycerols. It was found that the fatty acid composition of liver lipids depended markedly on the nature and the quantity of polyunsaturated fatty acid in the diet. The composition of the alkanes produced on stimulation of lipid peroxidation in vivo by inhalation of small, non-lethal doses of carbon tetrachloride corresponded closely to the fatty acid composition of the liver phospholipids. The results strongly suggest that the alkanes produced as a result of lipid peroxidation in vivo originate from the methyl end of the fatty acid administered. So ethane is produced from n-3 acid, propane from n-4 acid, pentane from n-6 acid and hexane from n-7 acid. The amounts of a specific alkane produced increase as its corresponding fatty acid, as present in the liver phospholipids, increases. There are indications that relatively more ethane than pentane is produced on stimulation of the in vivo lipid peroxidation although there are considerably more n-6 fatty acids than n-3 fatty acids present in the liver phospholipids.