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PubMed1976

Catechol estrogen formation by the human fetal brain and pituitary.

Homogenates of central neuroendocrine tissues from 2 male and 1 female midtrimester fetuses were incubated with (23H) estradiol-17beta. Metabolism at the C-2 position was monitored by measuring the tritium incorporated into water in the incubate. Liberation of tritium from the substrate by hypothalamus, limbic tissues, parietal cortex and pituitary occurred to the extent of 5.1-12.7%, 1.6-8.5%, 4.7-10.8%, and 0.9-4.1% of starting radioactivity, respectively. The nature of the product was confirmed by the isolation of 14C labelled 2-hydroxyestrone derivative from separate incubations with 14C-estrone as the substrate. With or without correction for weight of tissue incubated, catechol estrogen formation under these conditions occurs at levels similar to those seen in rat brain homogenates except that in contrast to the rat, the human cortex is also highly active.

Brain↗
PubMed1985

Autoradiographic determination of catechol estrogen binding sites in brain, pituitary and uterus.

The anatomical pattern of nuclear binding of 2-OH[6,9-3H]estradiol ([3H]2-OHE2) in brain, pituitary and uterus have been studied autoradiographically. Autoradiograms of forebrain, pituitary and uterus show nuclear concentrations of radioactivity in certain cells. This nuclear concentration is abolished when unlabelled 2-OHE2 or E2 was injected prior to the injection of [3H]2-OHE2. In the brain nuclear labelling is observed in the septal-preoptic region, in the anterior hypothalamic area, and in the central hypothalamic area. Some estrogen-sensitive nuclear groups, such as lateral septum and hippocampus, do not show accumulation of radioactivity. In the uterus, luminal and glandular epithelium, stromal cells and muscle cells are labelled. A comparison of the quantitative nuclear uptake of radioactivity and of the different time intervals after the injection of different doses shows similar uptake of nuclear radioactivity. This is comparable to data obtained after [6,7-3H]estradiol ([3H]E2) injection. The results provide clear evidence for nuclear binding of catechol estrogens of the same magnitude as [3H]E2 after in vivo treatment.

Animals↗
PubMed1987

[Hypocholesterolemic effect of catechol estrogen 2-monomethyl ether].

The hypocholesterolemic effect of 2-methoxyestrone (2-MeOE1), 2-methoxyestriol (2-MeOE3) and estradiol-17 beta (E2-17 beta) was investigated in two experimental systems of normocholesterolemic and dietary hypercholesterolemic rats that had undergone oophorectomy. Each compound was subcutaneously administered for 6 consecutive days at a dose of 10 micrograms per day in the former systems and at 300 micrograms per day in the latter system, respectively. The hypocholesterolemic effect was in the following relation: 2-MeOE3 = E2 - 17 beta greater than 2-MeOE1. In the latter system, the serum total cholesterol level of individual rats in both 2-MeOE3- and E2-17 beta-administered groups returned to normal. No uterotrophic activity was exhibited by either 2-MeOE1 or 2-MeOE3, while E2-17 beta exhibited an anomalous activity. The effect of 2-MeOE1 and 2-MeOE3 on body weight was not exhibited, while E2-17 beta reduced it slightly. The results suggest that catechol estrogen 2-monomethyl ether plays an important role in lipid metabolism through estrogen receptor independent mechanisms and has a pharmacologically important effect on hyperlipidemia and atherosclerosis.

Animals↗
PubMed1980

[Catechol estrogens].

Hydroxylation of oestrogens in the 2 or 4 positions leads to the formation of catechol oestrogens. These compounds are physiologically active in animals, especially in the control of gonadotropin secretion. Physiological activity can be ascribed to either an oestrogenic action or interaction with the catecholaminergic systems. These compounds are also formed in human subjects. Surprisingly high levels are found in the urine. The peri-ovulatory peak in urinary catechol oestrogen excretion is compatible with a role for these compounds in the control of gonadotropin secretion.

Animals↗
PubMed1988

Identification of microsomal, organic hydroperoxide-dependent catechol estrogen formation: comparison with NADPH-dependent mechanism.

Exogenous aromatic polycyclic hydrocarbons, notably benzo[a]pyrene, can be metabolized by both NADPH-dependent monooxygenase(s) and an organic hydroperoxide (OHP)-dependent mechanism. To determine whether phenolic estrogens, endogenous aromatic polycyclic hydrocarbons, can also be hydroxylated by these alternative pathways, conversion of estradiol (E2) to 2- and 4-hydroxylated catecholestrogens (2- and 4-OH-CEs) by human placental microsomes was examined under conditions previously shown to support CE formation by NADPH- and OHP-dependent mechanisms. CEs were formed under both conditions. Properties of OHP-dependent activity were similar to CE formation by peroxidases and distinct from the NADPH-dependent monooxygenase. NADPH supported only 2-hydroxylation, whereas cumene hydroperoxide supported 2- and 4-hydroxylation equally. Monooxygenase-mediated activity had characteristics of a high-affinity, low-capacity enzyme system (apparent Km for E2 = 0.3 microM, and Vmax = 31 pmol/mg protein/30 min), whereas peroxidatic activity had properties of low affinity and high capacity (apparent Km for E2 = 55 microM, Vmax = 666 pmol/mg protein/10 min). The requirement of peroxidatic activity for oxidizing co-substrate could be met by OHPs but not by H2O2. Peroxidatic CE formation could have special functional significance for physiological and pathological consequences of estrogen action since it generates 4-OH-CEs which are both effective catechols and potent, long-acting estrogens. Moreover, it could provide a link through co-oxygenation between estrogens and diverse cellular mechanisms involving generation of OHPs.

Carbon Dioxide↗
PubMed1982

The catechol estrogen, 2-hydroxyestradiol-17 alpha, is formed from estradiol-17 alpha by hypothalamic tissue in vitro and inhibits tyrosine hydroxylase.

The ability of estradiol-17 alpha to serve as a substrate for estrogen-2/4-hydroxylase in rabbit hypothalamic tissue was determined and compared to that of estradiol-17 beta. Both 2- and 4-hydroxy metabolites of estradiol-17 alpha were formed by the hypothalamic tissue in vitro. The rates of formation of 2-hydroxyestradiol (2-OHE2)-17 alpha and -17 beta were similar as were their kinetic constants (Km and Vmax). In addition, 2-OHE2-17 alpha was shown to inhibit purified rat adrenal tyrosine hydroxylase with a potency comparable to that of 2-OHE2-17 beta, a finding similar to that reported by others with respect to catechol-o-methyltransferase. Since estradiol-17 alpha has a markedly reduced affinity for estrogen receptors compared with extradiol-17 beta, this steroid could be useful in studies designed to distinguish between receptor mediated effects of estrogens and effects that locally formed catechol estrogens may have through their direct interaction with catecholaminergic system in neural tissue.

Animals↗
PubMed1976

Convenient large scale preparation of catechol estrogens.

2-Hydroxyestrone, 2-hydroxyestradiol-17beta, 2-hydroxy-17alpha-ethynylestradiol, 2-hydroxyestriol, 4-hydroxyestrone, 4-hydroxyestradiol-17beta, 4-hydroxy-17alpha-ethynylestradiol and 4-hydroxyestriol are prepared on a preparative scale from the corresponding aminophenols using a new inverse oxidation procedure. By the synthesis described both the 2- and 4-hydroxylated estrogens are available in high yields.

Catechols↗
PubMed1983

Catechol estrogens stimulate synthesis of prostaglandins in the preimplantation rabbit blastocyst and endometrium.

The influence of estradiol-17 beta (E2) or catechol estradiols [4-hydroxyestradiol-17 beta (4-OH-E2) or 2-hydroxyestradiol-17 beta (2-OH-E2)] on prostaglandin (PG) production in the rabbit blastocyst and endometrial cell in vitro on Day 6 of pregnancy (144 h postcoitum) was studied. Blastocysts (4-6) were incubated in 1 ml of RPMI-1640 medium for a total period of 8 h. Media were changed every 2 h and stored at -80 degrees C. E2, 4-OH-E2 or 2-OH-E2 at various concentrations were added during the second and fourth periods, while the vehicle was added during the first and third periods. Single cell suspensions of endometrial tissues in 0.5 ml of RPMI-1640 were incubated for 2 h with and without estrogens. The media and cells were separated and stored at -80 degrees C. PGs were determined by radioimmunoassay. The results for blastocyst were expressed as the cumulative release of PGs over a period of two 2-h incubations of the same experimental conditions (pg/blastocyst per 4 h). The release of PGs from the blastocyst was not influenced by 8.8 microM of 4-OH-E2, whereas 44 microM of this steroid stimulated the release of PGE-A by about 25% and PGF by 59% (P less than 0.05) over the vehicle-treated controls. The release of PGE-A and PGF in the presence of 44 microM of 2-OH-E2 was stimulated by about 60% and 37%. On the other hand, E2 at any concentration, either showed none or inhibitory effects on the release of PGs from the blastocyst.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

An assay for human erythrocyte catechol-O-methyltransferase activity using a catechol estrogen as the substrate.

A radiometric assay for catechol-O-methyltransferase (COMT) activity in human erythrocytes is described that employs 2-hydroxy[3H]estrone, and non-radiolabeled S-adenosylmethionine (SAM) as the cosubstrates. The ease of separation of the product of the reaction, 2-methoxy[3H]estrone from 2-hydroxy[3H]estrone makes it possible to achieve low reaction blanks. The assay is very sensitive, and only 200 microliter of whole blood are used per determination. The assay is highly reproducible. The interassay variability (coefficient of variation) was 6.5% for 24 assays of COMT activity in red blood cells in blood obtained daily for 24 days from one person. In incubations conducted at 37 degrees C for 30 min, the catechol-O-methyltransferase activity was a linear function of enzyme concentration (equivalent to 11 to 180 microliter of packed red blood cells). Employing this assay, we evaluated the catalytic conversion of 2-hydroxyestrone to 2-methoxyestrone by catechol-O-methyltransferase from human red blood cells and found that the apparent Michaelis constant and the apparent maximal rate of reaction were 3 x 10(-7) M and 6.7 x 10(-9) mol . ml-1 erythrocytes . h-1, respectively. The catechol-O-methyltransferase activity measured in erythrocytes obtained from 100 healthy subjects (men and nonpregnant women) was 8.2 +/- 0.17 (mean +/- S.E.) nmol 2-methoxyestrone . ml-1 erythrocytes . h-1.

Carbon Radioisotopes↗
PubMed2005

Genetic factors in catechol estrogen metabolism in relation to the risk of endometrial cancer.

2-Hydroxylated metabolites of estrogen have been shown to have antiangiogenic effects and inhibit tumor cell proliferation, whereas 4-hydroxylated metabolites have been implicated in carcinogenesis. We examined whether polymorphisms in certain genes involved in estrogen metabolism are associated with endometrial cancer risk in a population-based case-control study with 371 cases and 420 controls. Based on previously published genotype-phenotype correlation studies, we defined variant alleles thought to increase estrogen 2-hydroxylation as presumptively low-risk (CYP1A1 m1 T6235C and m2 Ile(462)Val) and those thought to increase estrogen 4-hydroxylation as high-risk (CYP1A1 m4 Thr(461)Asn, CYP1A2 A734C, and CYP1B1 Leu(432)Val). Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using unconditional logistic regression. Carrying at least one CYP1A1 m1 or m2 variant allele was associated with a decreased risk of endometrial cancer [ORs (95% CIs), 0.64 (0.44-0.93) and 0.54 (0.30-0.99), respectively]. No strong alteration in risk was observed among women with any of the putative high-risk alleles. When CYP1A1, CYP1A2, and CYP1B1 genotypes were combined and ranked by the number of putative low-risk genotypes carried, women with four or five low-risk genotypes had a reduced risk of endometrial cancer (OR, 0.29; 95% CI, 0.15-0.56) compared with women with one or none. No appreciable alteration in risk was observed among women carrying two or three low-risk genotypes. Some of our findings are consistent with the hypothesis that increased estrogen 2-hydroxylation is associated with decreased endometrial cancer risk, but replication of these results is required before any firm conclusions can be reached.

Aged↗