Physical and chemical changes in isolated chylomicrons: prevention by EDTA

When washed chylomicrons obtained from the lymph of rats, which had been fed corn oil, were maintained at 0-4 degrees C in 0.9% NaCl, the following physical and chemical changes were observed to occur: increased polarity of chylomicron lipids, increased ultraviolet absorption of chylomicron lipids at 232 nm, decreased linoleic acid content, and aggregation. These alterations occurred more rapidly at room temperature and were found to be associated with an increased lipid peroxide content. The behavior of isolated olive oil chylomicrons was qualitatively similar. All observed changes in the properties of washed chylomicrons were prevented by 0.25 mm EDTA; when tested, 25 micro m EDTA was equally effective. The changes were also prevented by 0.02% hydroquinone. The alterations in chylomicron lipids appear to result from the autoxidation of esterified linoleic acid. Studies with linoleic acid-U-(14)C-labeled chylomicrons indicated that cleavage of the linoleic acid carbon chain did not accompany the physicochemical changes. These results demonstrate the usefulness of EDTA in preventing these specific and progressive alterations in chylomicrons dispersed in aqueous systems.