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At least 109 records · Page 6Linked to original sources
PubMed1996

Synthesis of N-acetylcysteine conjugates of catechol estrogens.

The synthesis of N-acetylcysteine conjugates of 2-hydroxyestrone (2-OHE1) and 4-hydroxyestrone (4-OHE1) is described. The reaction of estrone 2,3-quinone with N-acetylcysteine provided 2-OHE1 and its C-4 and C-1 thioether conjugates in a ratio of 1:1, while estrone 3,4-quinone with N-acetylcysteine gave 4-OHE1 and its C-2 thioether conjugate as a sole product. Their structures were characterized by inspection of NMR spectra, chemical derivatization (methylation and acetylation), and comparison with the reactivity of 4-bromoestrone 2,3-quinone or 2-bromoestrone 3,4-quinone toward N-acetylcysteine.

Acetylcysteine↗
PubMed1991

Morphological effects of the catechol estrogens on rat epididymal epithelia.

The 2-hydroxy and 4-hydroxyestradiols (2-/4-OHE2) caused marked cytotoxic effects, including vacuolation and nuclear changes, in rat epididymal epithelia, after exposure to very low levels (40 ng/rat/week) for 20 weeks. The effects of the 2-/4-OHE2 metabolites were more pronounced than that of estradiol-17 beta (E2).

Animals↗
PubMed2002

Catechol estrogen formation in liver microsomes from female ACI and Sprague-Dawley rats: comparison of 2- and 4-hydroxylation revisited.

Estradiol (E(2))-hydroxylation was studied in liver microsomes from ACI and Sprague-Dawley female rats, which differ markedly in their susceptibility to E(2)-induced formation of mammary tumors. NADPH-dependent oxidation of E(2) by liver microsomes from ACI and Sprague-Dawley rats produced several metabolites of which 2-hydroxyestradiol (2-OH-E(2)), estrone (E(1)), and 2-hydroxyestrone (2-OH-E(1)) were predominant. Incubations with either low (9 nM) or high (50 microM) concentrations of radiolabeled E(2) and with varying amounts of microsomal protein indicated the formation of only small amounts of 4-hydroxyestradiol (4-OH-E(2)). The ratio of 2-OH-E(2) to 4-OH-E(2) formed with the low concentration of E(2) was about 10:1 regardless of the amount of microsomal protein used, and about 20:1 using a high concentration of E(2). Thus, oxidation of E(2) by liver microsomes from female ACI and Sprague-Dawley rats occurs primarily via 2-hydroxylation, and 4-hydroxylation is only a minor pathway. These results are in disagreement with a recent report indicating substantial 4-hydroxylation of E(2) by liver microsomes from female ACI rats.

Animals↗
PubMed1990

In vitro synthesis of prostaglandin E and F2 alpha by pig endometrium in the presence of estradiol, catechol estrogen and ascorbic acid.

These experiments were undertaken to determine the potential for estradiol-17 beta (E2), 2-hydroxyestradiol-17 beta (2-OH-E2) and 4-hydroxyestradiol-17 beta (4-OH-E2) to regulate prostaglandin (PG) E and F2 alpha synthesis by pig endometrium. Endometrium was collected from pigs on d 10 of pregnancy and incubated (15 to 20 mg/well) for three 2-h periods in 2 ml of medium in 24-well culture plates. At the end of each period, the medium was removed and frozen. Later media were thawed and assayed for PGE and PGF2 alpha. During Periods 2 and 3, the medium contained 0, 25, 50, 100 or 150 microM 2-OH-E2 (Exp. 1); 0, 25 or 50 microM 4-OH-E2 (Exp. 2); or 0, 25 or 50 microM E2 (Exp. 3). Each experiment was a factorial with 2-OH-E2, 4-OH-E2 or E2 as one main effect and 0 or 1 mM ascorbate as a second main effect. Ascorbate decreased (P less than .01) PGE and PGF2 alpha release in all experiments. Two-hydroxyestradiol-17 beta decreased (P less than .01) PGE and PGF2 alpha release into the medium during Periods 2 and 3 in a dose-dependent manner (Exp. 1). In Exp. 2, 4-OH-E2 decreased (P less than .07) endometrial release of PGE and PGF2 alpha in Periods 2 and 3 and increased (P less than .01) the PGE:PGF2 alpha in Period 3. In Exp. 3, E2 decreased release of PGE during Period 3 and PGF2 alpha release during Period 2. The PGE:PGF2 alpha was not altered by E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Catechol estrogens as inhibitors of leukotriene synthesis.

Estrogens have a beneficial effect on atherosclerosis and osteoporosis after menopause, but their exact mechanism of action is still unknown. The aim of the present study was to investigate the effects of estradiol and its metabolites catechol estrogens on arachidonic acid metabolism in vitro. Estradiol had no effect on arachidonic acid metabolism up to 33 microM in A23187-stimulated human whole blood. All catechol estrogens (2-hydroxyestradiol, 2-hydroxyestrone, 4-hydroxyestradiol and 4-hydroxyestrone) had similar kinds of actions on arachidonic acid metabolism, being over ten times more potent inhibitors of leukotriene synthesis (IC50 values 0.044-0.16 microM) than thromboxane (IC50 values 0.99-2.1 microM) and prostaglandin E2 synthesis (IC50 values 0.84-5.5 microM). It is suggested that some of the protective actions of estrogens--e.g., on atherosclerosis and osteoporosis--may be related to the inhibition of leukotriene synthesis by catechol estrogens.

Arachidonate 5-Lipoxygenase↗
PubMed1983

Selective chromatographic fractionation of catechol estrogens on anion exchangers in borate form.

The borate form of anion exchangers has been investigated for its utility in the field of estrogen analysis. The borate form of a weak (DEAE-Sephadex A-25) and a strong (QAE-Sephadex A-25) anion exchanger was easily prepared by appropriate washing of the gels, without the need of time consuming immobilization techniques. Estrogens with vicinal cis-hydroxyls were strongly retained in both gels through formation of borate complexes and readily separated from estrogens not possessing such groups. Moreover, borate complex formation with the labile o-dihydroxyphenyl moiety of catechol estrogens fully protected them from decomposition during chromatography. Quantitative recovery of catechol estrogens was thereby obtained without use of antioxidants. The borate form of QAE-Sephadex A-25 was capable, in addition, of separating estrogens not possessing vicinal cis-hydroxyls from the corresponding neutral steroids.

Anion Exchange Resins↗
PubMed1986

Catechol estrogen formation by the CNS: regional distribution of estrogen-2/4-hydroxylase activity in rat brain.

Estrogen-2/4-hydroxylase (E-2/4-H) activity was measured by a direct product isolation assay in punch biopsy specimens obtained from nine nuclear regions from forebrain of adult male rats. Tritiated catechol estrogens were isolated from incubations of tissues with [6,7-3H]estradiol from all regions studied. The amount of 4-hydroxyestradiol (4-OH-E2) formed equaled or exceeded that of 2-hydroxyestradiol (2-OH-E2). There were significant regional differences in the amounts of catechol estrogen produced. The difference was nearly 8-fold between the arcuate-median eminence (ARC-ME) and the medial preoptic nucleus (POM), regions with the highest and lowest specific activities, respectively (37.7 +/- 6.2 vs. 5.1 +/- 0.7 pmol/mg protein/10 min 2-OH-E2, mean + SEM, n = 6). The supraoptic nucleus was the site of second highest concentrations of E-2/4-H activity (20.3 pmol 2-OH-E2/mg protein/10 min). Estrogen-2/4-H activity in the paraventricular (PVN) and periventricular (PERI) nuclear regions, though only about half that in the SON, was significantly greater than in the remaining brain areas (nucleus interstitialis striae terminalis, caudate, anterior hypothalamic and medial preoptic nuclei and cortex. The ARC-ME, the region with the highest E-2/4-H activity is where the dopaminergic neurones and terminals from the Gn-RH neurons are concentrated. The functions regulated by these two classes of neurones, the secretion of prolactin and gonadotrophins, respectively, have been the subject of most of the previous studies aimed at establishing the role of catechol estrogen formation in the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗