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At least 1,135 records · Page 63Linked to original sources
PubMed1986

Regioselective reaction of thiols with catechol estrogens and estrogen-O-quinones.

Incubations of [3H]estradiol and [3H]2-hydroxyestradiol (2-OHE2) with rat liver microsomes and mushroom tyrosinase were carried out in the presence of glutathione and 2-mercaptoethanol. A ratio of about 3.5:1 for the C-4 and C-1 thioether conjugates of 2-OHE2 was observed. Chemical reaction of estradiol-2, 3-O-quinone with various thiols showed that alkyl and phenyl thiols gave about a 1:1 ratio of C-4 to C-1 thioethers. However, reaction of the O-quinone with 4-nitrothiophenol gave a C-4/C-1 ratio of 0.25 while 4-bromothiophenol gave a C-4/C-1 ratio of 4.0. These studies suggest that the regioselectivity of the reaction of thiols with estrogen catechols and O-quinones may be dependent on the nature of the thiol compounds and less on steric hindrance.

Animals↗
PubMed1990

In vitro metabolism of catechol estrogens by human fecal microflora.

Intestinal bacterial metabolism of the catechol estrogens, 2-hydroxyestrone (2-OHE1), 2-methoxyestrone (2-MeOE1) and 2-hydroxyestradiol (2-OHE2), was studied by incubation of the steroid with mixed fecal flora. 3-Methoxyestrone (3-MeOE1) was included in order to evaluate whether demethylation occurs also with regard to noncatecholic estrogens. The purification of the samples and separation into fractions was carried out by ion exchange chromatography and the metabolites formed were identified by combined gas chromatography-mass spectrometry (GC-MS). Mixed human fecal flora was able to interconvert 2-OHE1 and 2-OHE2 both in aerobic and anaerobic conditions. Demethylation occurred both for 2-MeOE1 and 3-MeOE1.

Chromatography, Ion Exchange↗
PubMed1982

Catechol estradiol induced implantation in the mouse.

Induction of implantation is among the most sensitive responses to estrogens. The ability of catechol estradiols, 4-hydroxy-estradiol-17 beta (4-OH-E2) and 2-hydroxy-estradiol-17 beta (2-OH-E2), to induce implantation in ovariectomized pregnant mice was compared to that of estradiol-17 beta. Delayed implantation was maintained by the daily administration of 2 mg of progesterone. A single injection of 3 ng of estradiol-17 beta, 50 ng of 4-OH-E2, or 2,000 ng of 2-OH-32 consistently induce a full complement of implantation sites in all animals. Before the estrogenicity of the latter steroid can be established the lack of contaminating estrogens must be proved.

Animals↗
PubMed1983

O-methylation of dopamine-o-sulfates with catechol-0-methyltransferase.

[2H2]-dopamine-3-0-sulfate (DM-3-0-S) and [2H2]-dopamine-4-0-sulfate (DM-4-0-S) were synthesized to investigate the possibility of their being substrates for catechol-0-methyltransferase (COMT). [2H5]-3-0-methyldopamine (3-0-Me-DM) and [2H5]-4-0-methyldopamine (4-0-Me-DM) were also synthesized as internal standards for the determination of enzymatic products by gas chromatography-mass spectrometry (GC-MS). [2H2]-DM-3-0-S or [2H2]-DM-4-0-S was incubated at 37 degrees for 60 min in the presence of S-adenosyl-L-methionine with a crude enzyme preparation obtained from rat liver homogenate. The incubation mixture was treated with 0.5N HCl at 100 degrees C for 1h to hydrolyze the remaining sulfate moiety. The reaction products were extracted with an Amberlite XAD-4, derivatized with pentafluoropropionic anhydride and determined by GC-MS. When [2H2]-DM-3-0-S was used as a substrate, [2H2]-3-0-Me-DM was found to be a major product accompanied by [2H2]-4-0-Me-DM as a minor product. The ratio of [2H2]-3-0-Me-DM to [2H2]-4-0-Me-DM was found to be 26:1, while the ratio was 5.4:1 when [2H2]-dopamine was used as a substrate. When [2H2]-DM-4-0-S served as a substrate, [2H2]-3-0-Me-DM was preferentially produced without detectable formation of [2H2]-4-0-Me-DM.

Animals↗
PubMed1988

Properties of novel effective and highly selective inhibitors of catechol-O-methyltransferase.

Novel bisubstituted catechols were found to be potent and highly selective COMT inhibitors in vitro. One of them, OR-462 (3-(3,4-dihydroxy-5-benzylidene)-2,4-pentanedione), was studied also in vivo. When administered to rats orally together with levodopa and carbidopa, OR-462 greatly improved the bioavailability of levodopa and effectively reduced the formation of 3OMD. The levels of levodopa and dopamine were increased also in the striatum, and the 3OMD levels were decreased. The metabolic profile of dopamine demonstrated that COMT inhibition occurred in the peripheral tissues but not in the striatum. OR-462 thus resembled the peripheral inhibitors of dopadecarboxylase. These potent, selective and orally active COMT inhibitors offer a new tool for interfering in the metabolism of various COMT substrates.

Animals↗
PubMed1988

Catechol-O-methyltransferase activity in human and rat small intestine.

The activities of soluble (S-COMT) and membrane-bound (MB-COMT) forms of catechol-O-methyltransferase in different regions of human and rat small intestine were determined. S-COMT was the predominant form both in the mucous membrane and in the muscle layers. The activity of S-COMT was more than twice as high in the mucous membrane as in the muscle layer. The activity of MB-COMT was almost equal in the different regions of the gut as well as in the mucous membrane and muscle layers. However, the ratio of the soluble form to the membrane-bound form was close to one in the human muscle layers of the jejunum and ileum.

Animals↗
PubMed1991

Catechol-O-methyltransferase and aromatic L-amino acid decarboxylase activities in human gastrointestinal tissues.

Human gastrointestinal samples from the corpus, antrum, bulbus, jejunum and ileum were assayed for soluble and membrane-bound catechol-O-methyltransferase (COMT) and aromatic L-amino acid decarboxylase (AADC) activity in vitro. The mean soluble COMT activities with 3,4-dihydroxybenzoic acid (DBA) and 3,4-dihydroxyphenylalanine (L-DOPA) as substrate were 70-242 and 70-174 pmol/min mg, respectively. The membrane-bound COMT activities ranged from 33 to 60 pmol/min mg in the different parts of the intestine. The AADC activities, measured with L-DOPA as the substrate, increased from 114 pmol/min mg in the corpus to 3488 pmol/min mg in the jejunum. The affinity of the soluble COMT was approximately 20 times higher for DBA (Km 15-19 microM) than for L-DOPA (Km 300-600 microM). The Km-values for L-DOPA of AADC and COMT were of the same order of magnitude. The specific COMT inhibitors, nitecapone and OR-611, effectively inhibited in vitro the human intestinal COMT activity. Nanomolar concentrations caused 50% inhibition with both DBA and L-DOPA as substrate.

Aromatic-L-Amino-Acid Decarboxylases↗
PubMed1992

Electrophoretic analysis of low and high activity forms of catechol-O-methyltransferase in human erythrocytes.

Analysis of the catechol-O-methyltransferase (COMT) enzyme in human RBC lysates from 15 samples exhibiting inherited variations in level of activity and thermal stability was performed. Electrophoretic blotting and immune fixation was carried out following sodium dodecyl sulfate polyacrylamide gel electrophoresis or isoelectric focusing of lysate protein. These techniques did not reveal a major structural alteration of the protein that could account for the observed variation in enzyme activity or thermal stability. Future studies utilizing molecular genetic techniques should make it possible to determine the basis for inherited variations in human RBC COMT activity and thermal stability.

Catechol O-Methyltransferase↗
PubMed1991

Effects of inhibition of monoamine oxidase on the levels of 5-S-cysteinyl adducts of catechols in dopaminergic regions of the brain of the guinea pig.

The occurrence of 5-S-cysteinyl adducts of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylalanine (DOPA) in brain tissue, appears to reflect in vivo autoxidation of DA, DOPA and DOPAC, respectively. In the striatum and in the limbic system of guinea pig, the levels of DOPAC and 5-S-cysteinyl-DOPAC were markedly reduced after treatment with pargyline (75 mg/kg, i.p., 17 hr) and pargyline plus reserpine (75 mg/kg, i.p., 17 hr plus 5 mg/kg, i.p., 18 hr) compared to controls. However, the depletion of 5-S-cysteinyl adduct was less severe than that of DOPAC, suggesting a slower turnover of the adduct. Dopamine and 5-S-cysteinyl-DA increased significantly and to the same extent in the striatum, after pargyline alone. In the limbic system DA was significantly increased, whereas no change was found for levels of 5-S-cysteinyl-DA. 5-S-Cysteinyl-DOPA decreased significantly in the striatum after treatment with pargyline plus reserpine and non-significantly after pargyline alone. The data are compatible with a slight inhibitory effect of MAO inhibition on catechol autoxidation. This effect was, however, overridden by the increased level of DA.

3,4-Dihydroxyphenylacetic Acid↗
PubMedDate not supplied

Increased urinary catechol estrogen excretion in female smokers.

Premenopausal female smokers show significantly increased estrogen 2-hydroxylation, which may account in part for the anti-estrogenic effects of cigarette smoking. We have measured five major urinary estrogens, including estradiol (E2), estrone (E1), 16 alpha-hydroxyestrone (16 alpha OHE1), estriol (E3), and 2-hydroxyestrone (2OHE1), in premenopausal female smokers and non-smokers, to determine whether increased C-2 hydroxylation affected the urinary excretory patterns in these subjects. While total measured estrogen excretion in the follicular phase did not differ significantly between the two groups, urinary 2OHE1 among the smokers constituted a significantly greater proportion of the total (31.1 vs 18.2%, P less than 0.02). This difference was largely caused by significantly increased urinary 2OHE1 and decreased E3 observed in smokers. A urinary catechol estrogen index, defined by [2OHE1]/[E3], was significantly elevated in smokers compared with non-smokers (1.67 +/- 0.21 vs 0.56 +/- 0.08, P less than 0.001), and this urinary index correlated strongly with radiometrically determined estrogen 2-hydroxylation (r = 0.84, P less than 0.01). Ratios of the various estrogen metabolites did not vary substantially throughout the menstrual cycle. Urinary estrogen indices as described here may therefore be useful in demonstrating differences in estrogen metabolism, specifically 2-hydroxylation vs 16 alpha-hydroxylation, in selected populations.

Adult↗
PubMed1994

Catechol estrogen production in rat microsomes after treatment with indole-3-carbinol, ascorbigen, or beta-naphthaflavone: a comparison of stable isotope dilution gas chromatography-mass spectrometry and radiometric methods.

Compounds like indole-3-carbinol (I3C) have been shown to increase catechol estrogen formation and reduce mammary tumor incidence in mice. These compounds may exert a protective effect for breast cancer development by decreasing the overall estrogen pool available for the formation of 16 alpha-hydroxyestrone (16 alpha-OHE1), a metabolite that retains significant estrogenic activity, may be mutagenic and could represent a potential carcinogenic intermediate of estradiol degradation. I3C and ascorbigen originate from the breakdown of glucobrassicin. We have compared the inductive effects of I3C with ascorbigen and beta-naphthaflavone (Bnf) in microsomes from rats pretreated with these compounds using isotope dilution GC-MS and a radiometric method. Incubated microsomes from rats pretreated with I3C and ascorbigen yielded high levels of 2-hydroxyestradiol (2-OHE2) that were comparable to levels induced by Bnf and were significantly above control group levels (p < 0.005). Absolute values determined by the radiometric method were approximately 40% lower than 2-OHE2 concentrations determined by GC-MS, although the relative changes in each group were the same. These differences may be attributed to the radiolabel becoming trapped in microsomal intermediates in the sequence leading to tritium entering the aqueous compartment. Both ascorbigen- and Bnf-treated animals exhibited significant increases in 2-hydroxyestrone (2-OHE1) (p < 0.05). The ability of ascorbigen to induce estradiol C-2 hydroxylation has not been previously reported. Based on these data, we speculate that ascorbigen will act as an anticarcinogenic agent and will inhibit or reduce the incidence of mammary tumor formation.

Animals↗
PubMed1986

beta-phenylethylamine effect on brain and blood catechol-O-methyltransferase activity.

A significant decrease in catechol-o-methyltransferase (COMT) activity has been found in the striatum (77% of control) and hippocampus (63% of control) of gerbils treated with daily injections of beta-phenylethylamine (50 mg/kg) for 10 days. This treatment group also exhibited increased (204% above control) COMT activity in a lysed red blood cell preparation. There were no changes in COMT activity in groups receiving 10 mg/kg beta-phenylethylamine or haloperidol (0.5 mg/kg). In vitro beta-phenylethylamine has no demonstrable effect on COMT activity.

Animals↗
PubMed1990

Selection of independent plasmids determining phenol degradation in Pseudomonas putida and the cloning and expression of genes encoding phenol monooxygenase and catechol 1,2-dioxygenase.

Long-term cultivation of the Pseudomonas putida multiplasmid strain EST1020 on phenol resulted in the formation of individual PHE plasmids determining phenol degradation. Four types of PHE plasmids, pEST1024, pEST1026, pEST1028, and pEST1029, are characterized. They all contain a transferrable replicon similar to pWWO-8 with a partly duplicated DNA sequence of the 17-kb transposable element of this plasmid and include various amounts of DNA that carry genes encoding phenol degradation (phe genes). We cloned the genes determining phenol monooxygenase and catechol 1,2-dioxygenase from the Pseudomonas sp. parent strain plasmid DNA into the broad host range vector pAYC32 and studied the expression of the cloned DNA. The formation of a new hybrid metabolic plasmid, pEST1354, was demonstrated in P. putida PaW85 as the result of transposition of the 17-kb genetic element from the chromosome of PaW85 into the plasmid carrying cloned phe genes. The target site for the 17-kb transposon was localized in the vector DNA, just near the cloning site. In subcloning experiments we found two regions in the 17-kb DNA stretch that are involved in the expression of the cloned phe genes.

Catechol 1,2-Dioxygenase↗
PubMed1980

Catechol-O-methyltransferase and catecholamines in anxiety and relaxation.

Levels of anxiety, plasma epinephrine and norpinephrine, and red blood cell (RBC) catechol-O-methyltransferase (COMT) activity were measured before and after 4 weeks of relaxation training in a group of 15 drug-free, anxious subjects and at a similar interval in a group of 15 drug-free, healthy controls. The index group showed significant decreases in levels of anxiety and plasma epinephrine and norepinephrine after treatment. No changes were observed in the control values. RBC COMT did not show any significant differences in activity between the index and control groups and between the pre- and posttreatment values. Similarly, COMT activity levels failed to correlate with levels of anxiety and catecholamines before or after treatment. These findings indicate that anxiety is unlikely to have an effect on RBC COMT activity, whereas it has a direct effect on plasma catecholamines.

Adult↗
PubMed1980

Monoamine oxidase and catechol-O-methyltransferase activities in cultured fibroblasts and blood cells from children with autism and the Gilles de la Tourette syndrome.

Monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) activities were measured in cells from children with autism (n = 5) and the Gilles de la Tourette syndrome (n = 5). Monoamine oxidase activities in cultured skin fibroblasts (type A) and platelets (type B) from the same individual were not correlated. COMT activities in fibroblasts and red blood cells showed a negative but not significant correlation (r = -0.42). Fibroblast MAO and COMT activities from patients were similar to values from controls matched for age, race, and sex. Increasing clinical severity of illness in both disorders, however, correlated significantly with higher fibroblast MAE activity. Cultured fibroblasts provide a means of measuring enzyme activities independently of the individual's current physiological and psychological state.

Adolescent↗
PubMed1981

Catechol-O-methyltransferase of erythrocytes in patients with endogenous psychoses.

A significant decrease in catechol-O-methyltransferase (COMT) activity of erythrocytes was found in both male and female schizophrenic patients, as well as in male patients with schizophreniform psychosis. Among control subjects, a sex difference in COMT activity of erythrocytes was found, with males showing significantly higher activity than females. It is suggested that a genetically determined deficiency of catecholamine degradative enzymes in the central nervous system or, alternatively, influences of nongenetic hormonal factors could be implicated in the findings of altered erythrocyte COMT activity reported.

Adult↗
PubMed1989

Plasma levels of catechols after fasting in intact or adrenal-demedullated rats.

We compared arterial plasma levels of catechols after a 24-h fast with levels after 24 h of an ad libitum diet in conscious rats. Epinephrine concentrations were significantly decreased after the fast; levels of norepinephrine, dopa, and dihydroxyphenylglycol were unaffected. Adrenal-demedullated rats had decreased levels of dopa regardless of dietary intake and lower levels of norepinephrine after fasting than during the usual diet. The results indicate that fasting decreases adrenomedullary activity in intact animals, with little or no effect on sympathoneural activity.

Adrenal Medulla↗
PubMed1992

Expression of enzymatically active rat liver and human placental catechol-O-methyltransferase in Escherichia coli; purification and partial characterization of the enzyme.

To produce sufficient amounts of recombinant catechol-O-methyltransferase (COMT) for structural and functional studies the coding regions of the rat liver and human placental COMT genes have been introduced into a bacterial expression vector pKEX14. Recombinant COMT was produced in Escherichia coli up to 10% of total bacterial protein after the induction of the T7 RNA polymerase gene with isopropyl-beta-D-thiogalactopyranoside. Both the rat and human enzymes were enzymatically active, soluble and reacted with anti-COMT antiserum in Western blotting. Both enzymes were purified from E. coli cells and partially characterized by determining their specific activity, apparent molecular weight and pI.

Animals↗