Stoffwechsel und Wirkungsmechanismus der Östrogene, X. Beziehungen zwischen Östrogenstoffwechsel und Lipidperoxydation in Rattenlebermikrosomen

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Abstract
The metabolism of estrone by rat liver microsomes/NADPH, and the microsomal peroxidation of unsaturated fatty acids (lipid peroxidation) compete for a common factor. 2-Hydroxyestrone is an intermediate in the formation of protein-bound and water soluble metabolites of estrone; this process and lipid peroxidation are stimulated in parallel. The conversion of estrone or 2-hydroxyestrone into protein-bound metabolites can occur in 3 different ways: by an enzymatic reaction, which is not blocked by EDTA and probably involves cytochrome P-450; by a reaction, which is activated by Fe2 and inhibited by EDTA and is catalyzed by the enzyme system responsible for microsomal lipid peroxidation; pathway b appears to replace pathway a, especially in older rats; by a non-enzymatic reaction, which, together with the non-enzymatic peroxidation of lipid, is stimulated by high concentrations of Fe20 and does not require NADPH.