Abstract
A purpose-built apparatus has been developed to determine ethane, pentane and other hydrocarbons exhaled by laboratory rodents, as an index of lipid peroxidation. The GC method was optimised to decrease interference from the greater quantities of acetone in the breath, and methane from the gastro-intestinal tract. Administration of phenylhydrazine to rat resulted in exhalation of propane and other hydrocarbons. These gases, when injected into the apparatus, were metabolised faster by mice than rats. Quantitation of ethane exhalation provided the most reliable measure of lipid peroxidation in vivo because pentane, and other hydrocarbons were more extensively metabolised. Several compounds causing lipid peroxidation in mouse were investigated by this method, and the time course and dose response of ethane exhalation, and the associated malondialdehyde (MDA) production following administration of the most potent of these, iron nitrilotriacetate (FeNTA) were studied. MDA production was greater, and showed better correlation with ethane exhalation, in kidney than liver. Administration of FeNTA to rat resulted in greater MDA production in liver than kidney and caused haematological changes. Histological damage appeared in rat and mouse kidney after dosing with FeNTA, and correlated well with ethane exhalation; renal tubule brush border marker enzymes were also decreased by FeNTA. Some animals treated with Fe NTA showed hepatic necrosis. Sub-chronic administration of FeNTA to rats was compared with dietary administration of iron and parenteral iron dextran. FeNTA was the most effective and caused severe kidney necrosis, loss of hepatic mixed function oxidase and glutathione peroxidase activities and haematological changes. Buthionine sulphoximine, which depletes glutathione, increased Fe NTA-induced lipid peroxidation in rat and mouse. Pretreatment with furosemide, desferrioxamine, or hypoxia, decreased Fe NTA-induced lipid peroxidation in mouse. Dietary vitamin E-deficiency, or BHT supplementation gave equivocal results with Fe NTA or tert-butyl hydroperoxide-induced lipid peroxidation.