LIPID PEROXIDE FORMATION AND PHOSPHOLIPID IN NORMAL AND TUMOR TISSUES
1958 Volume 49 Issue 4 Pages 233-248
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1958 Volume 49 Issue 4 Pages 233-248
1. Homogenates of normal and tumor tissues were respectively fractionated into lipid and residue (protein) fractions and these fractions were examined for lipid peroxide forming activity. It was found that whereas neither the lipid nor residue fraction alone showed apperciable activity, the combination of both fractions invariably showed a high peroxide value, at least in the case of normal tissues.
2. Lipid which is responsible for the peroxide formation was found to be phospholipid.
3. When the residue fraction was dialyzed, the peroxide forming activity was no longer observed even after the addition of an active lipid fraction, suggesting the persence of a dialyzable cofactor in the residue. It was therefore concluded that for the production of lipid peroxide a phospholipid and a cofactor are essential together with zinc.
4. Iron alone could activate the lipid peroxide formation in whole homogenates or lipid fractions, although zinc has been found to be the only metal which can restore the activity in EDTA-treated homogenates.
5. A comparison of the activity of peroxide formation was made in various reciprocal combinations (tumor fractions×fractions of normal liver). Having confirmed that capability of peroxide formation is nearly all lost in tumor tissues, it was further found that the peroxide value was greatly decreased when tumor lipid was added to the residue of normal liver.
6. Reduced activity in tumor tissues with respect to peroxide formation is not due to the presence of antioxidants.
7. Suggestions were put forward that as the result of neoplasia some qualitative changes in phospholipid occur and at the same time zinc becomes firmly bound to cell structures and no longer available for the reaction, these changes leading to an overall inhibition of the lipid peroxide formation in tumor tissues.
8. The general impression was obtained that the tumor tissue is different from normal in the nature of phospholipid constituents, and that the modification or the lack of certain phospholipids constitute an important characterization of the tumor tissue.
