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H Breuer

Publications and source records attributed to H Breuer.

At least 181 records · Page 10Linked to original sources
PubMed1974

Chemical and biochemical studies on 18-hydroxyoestrone.

1. 18-Hydroxyoestrone was reduced by NaBH(4) in methanol, giving 18-hydroxyoestradiol-17alpha and 18-hydroxyoestradiol-17beta in the ratio 3:7. 2. Treatment of 18-hydroxyoestrone with a strong alkali yielded 18-noroestrone; however, the 18-hydroxyoestradiols did not undergo transformation to their respective 18-nor derivatives. 3. All the 18-hydroxylated oestrogens were stable under acid conditions. They formed Kober chromogens: the chromogenicity of 18-hydroxyoestrone was only one-third that of the 18-hydroxyoestradiols and oestriol. 4. Paper-, thin-layer- and gas-liquid-chromatographic systems for the characterization of these compounds are described. 5. An examination of the mass spectra revealed peaks characteristic of the substituted carbon atoms. Definite assignment of the 17alpha- and 17beta-hydroxyl groups of the epimeric 18-hydroxyoestrogens was possible by characteristic fragmentation of the free steroids. Further, the configuration of 18-hydroxyoestradiol-17beta was confirmed by the formation of the dimethylsildioxy derivative of the 3-methylether of the steroid. 6. Both rat and rabbit liver slices reduced 18-hydroxyoestrone to 18-hydroxyoestradiol-17beta and some other labile, polar metabolites with properties similar to 2-hydroxylated oestrogens. No formation of 18-hydroxyoestradiol-17alpha in vitro was observed. 7. The results are discussed with respect to the possible influence of the 18-hydroxyl group on reactions at C-17, as well as the reactions of 18-hydroxylated oestrogens with strong acid (Kober reactions) and alkali.

Animals↗
PubMed1974

Influence of an 18-hydroxyl group on the interaction of oestrogens and hydroxysteroid oxidoreductases.

1. Partially purified 17beta-hydroxy steroid-NAD(+) oxidoreductases, prepared from Pseudomonas testosteroni (EC 1.1.1.51), human term placenta (EC 1.1.1.62) and the cytoplasmic fraction of rat liver (EC 1.1.1.-) were tested for their ability to catalyse the oxidoreduction of 18-hydroxyoestradiol-17beta and 18-hydroxyoestrone. The products of incubation were identified by chromatographic procedures and by mass spectrometry. 2. The Pseudomonas enzyme catalysed both the oxidation of 18-hydroxyoestradiol-17beta and the reduction of 18-hydroxyoestrone; in contrast, the placental and rat liver enzymes only catalysed the reduction of 18-hydroxyoestrone. 3. These results were confirmed, by using a spectrophotometric assay; equimolar quantities of oestradiol-17beta and 18-hydroxyoestradiol-17beta were oxidized at approximately the same rate by the microbial enzyme. 4. These findings suggest that 18-hydroxyoestradiol-17beta may be a normal oestrogen metabolite. 5. The differences in ability of the mammalian and microbial enzymes to metabolize 18-hydroxylated oestrogens is explained on the basis of recognition sites with different geometrical dimensions, characteristic of the placental (Descomps & Crastes de Paulet, 1969) and the microbial steroid enzymes (Fosset & Crastes de Paulet, 1967).

Animals↗