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PubMed1987

Metabolism of 6,7-dimethoxy 4-(4'-chlorobenzyl)isoquinoline. II. Role of liver catechol O-methyltransferase and glutathione.

1. On i.v. administration to rats of 14C-6,7-dimethoxy 4-(4'-chlorobenzyl)isoquinoline (PV2) 23% dose of 14C was excreted in urine and 72% in faeces. The pattern of metabolites showed ten 14C-PV2 derivatives and unchanged PV2. Seven metabolites have been characterized by comparison with authentic compounds e.g. the ketone of PV2, the N-oxide PV2, the demethylated metabolites 6-hydroxy-PV2, 7-hydroxy-PV2 and 6,7-dihydroxy PV2, the benzyl ring-hydroxylated metabolites, 3'-hydroxy-PV2 and 6,7,3'-trihydroxy-PV2. Unchanged PV2 and its metabolites are excreted both free and conjugated. 2. Enzymic O-methylation of 6,7-dihydroxy-PV2 by liver catechol-O-methyl transferase (COMT) in vitro produced 6-hydroxy,7-methoxy-PV2. After blockade of COMT by pyrogallol in vivo, the excretion of 6,7-dihydroxy-PV2 was increased and the excretion of 6-hydroxy, 7-methoxy-PV2 decreased. 3. Hydroxylation of the benzyl ring of PV2 and its metabolites indicates the formation of an intermediate epoxide followed by glutathione conjugation. After glutathione depletion in vivo by diethyl maleate (DEM) liver covalent binding of 14C-PV2 metabolites was increased and biliary excretion of benzyl ring-hydroxylated PV2 metabolites decreased. Replacement of glutathione depletion by a cysteine derivative restored liver covalent binding and the excretion of PV2 metabolites to levels similar to those observed in control rats, indicating that glutathione conjugation may be an important metabolic pathway for the detoxication of PV2 and its metabolites in vivo.

Animals↗
PubMed1999

In vitro methylation of arsenite by rabbit liver cytosol: effect of metal ions, metal chelating agents, methyltransferase inhibitors and uremic toxins.

The methylation of carrier-free 74As-arsenite by liver cytosol of Flemish Giant rabbits is highly susceptible to additions of trace elements. In vitro supplementation of essential trace elements like zinc (Zn2+), vanadium (V5+), iron (Fe2+), copper (Cu2+) and selenate was shown to increase the methylation efficiency. Trivalent metal ions (e.g. Al3+, Cr3+ and Fe3+), Hg2+, Tl+ and SeO3(2-) had a deleterious effect. The inhibitory effect of EDTA, oxime and many divalent cations (Ca2+, Mg2+, Sr2+, ...) suggest a co-factor role for a specific divalent metal ion, possibly Zn2+. Chelating agents used in clinical treatment of acute and chronic inorganic arsenic poisoning lower the methylation capacity of cytosol by rendering the trivalent arsenic unavailable for the methyltransferase enzymes. S-adenosylhomocysteine and periodate-oxidized adenosine, inhibitors of s-adenosylmethionine dependent methylation pathways, inhibit the methylation of arsenite. Pyrogallol, a catechol-O-methyltransferase inhibitor, blocks the action of arsenite- and monomethylarsonic methyltransferase enzymes, suggesting a close structural relationship between the active sites of the different enzymes. Some uraemic toxins, namely oxalate, p-cresol, hypoxanthine, homocysteine and myo-inositol, inhibit arsenic methylation.

Animals↗
PubMed1999

Effects of oxidative damage of membrane protein thiol groups on erythrocyte membrane viscoelasticities.

In three oxidative damaging systems: the diamide-mercaptoethanol redox modification system (DM), the pyrogallol oxygen free radicals system (PG) and the hypoxanthine-xanthine oxidase oxygen free radical system (HXO), the effect of erythrocyte membrane oxidative damage on membrane viscoelasticities was investigated with micropipette aspiration method. The experimental results indicated that erythrocyte membrane oxidative damage has a great influence upon the membrane mechanical properties. The oxidative damage led to decrease of contents of membrane protein thiol radical. The scanning of SDS-PAGE presented that membrane proteins form the higher molecular weight component (HMP) by the cross-linking of membrane protein thiol radicals that might hinder the conformational change of membrane protein. This might be the reason for the increased membrane elastic modulus and viscous coefficient upon treating erythrocytes with the oxidative damaging systems. A significant negative logarithm regression relation was found between the membrane elastic modulus, mu, or viscoefficient, eta, and the contents of membrane protein thiol radicals. These experimental results suggested that thiol radicals oxidative damage reaction due to the superoxides anions (*O2-) may be an important molecular mechanism inducing changes of membrane viscoelasticities or whole cell deformability of erythrocyte under physiological and pathological oxidative stress.

Blood Viscosity↗
PubMed2000

Protein determination in cerebrospinal fluid by protein dye-binding assay.

In this study, Coomassie brilliant blue (CBB) and pyrogallol red/molybdate (PRM) protein dye-binding assays for total protein determination in cerebrospinal fluid (CSF) are compared. Using human albumin (HA) as a protein calibrator, protein concentration in CSF samples (n = 73) ranged from 55-1960 mg/L (median: 315 mg/L) with the CBB assay, and from 95-2450 mg/L (median: 395 mg/L) with the PRM assay. Linear regression analysis indicated yCBB = 0.824xPRM - 8 (r = 0.99). The discrepancy between the values was investigated by comparing the response of the two assays to different proteins. Compared with HA, the PRM assay showed a more uniform response to human albumin/globulin (A/G) and bovine gamma globulin (G) than did the CBB assay, but it gave high colour yields with bovine myelin basic protein. When CSF was assayed using A/G as a protein calibrator, agreement between the methods improved (yCBB = 0.960xPRM + 0 [r = 0.99]), indicating that comparability is dictated by the choice of protein calibrator. Of the two assays studied, the PRM assay is recommended for CSF protein determination because it gives a more uniform and linear response to human albumin and globulin over a wider working range.

Animals↗
PubMed1975

[Experimental exophthalmos. Preliminary communication].

Pyrogallol and N1-(d,1-seryl)-N2-(2,3,4-trihydroxy-benzyl)-hydrazine (RO-4-4602), two inhibitors of catechol-O-methyl-transferase, produce exophthalmus in mice and rats. This exophthalmus can be suppressed by local application of guanethidine.

Animals↗
PubMed2004

[Superoxide dismutase biosensor for screening substances possessing scavenging superoxide anion activity].

AIM: To establish a method for screening active substance with scavenging effects on superoxide anion in vitro by designed superoxide dismutase biosensor. METHODS: The enzyme sensor was built by connecting the immobilized CuZnSOD with optical oxygen sensor through a special way. Superoxide anions were generated by auto-oxidation of pyrogallol. The auto-oxidation speed was examined before and after adding samples into the system, and the Vit C having the scavenging radical activities was served as a positive control. RESULTS: The limit of biosensor detection was 7.0 U in activity, and lifetime of the immobilized enzyme in the reaction-cell was above 2 weeks. The scavenging effects on superoxide radicals of fifteen active substance were studied in vitro by the sensor, and some of them presented scavenging activities. CONCLUSION: The signal from biosensor is stable, easy to be determined, and the kinetic information on scavenging superoxide radicals could be obtained directly. The biosensor system can be used for screening drugs simply and rapidly.

Ascorbic Acid↗
PubMed1976

[Purification and properties of peroxidase from tea leaves].

Purification of fractions of tea leaves peroxidase is described. During ion-exchange chromatography on DEAE- and CM-cellulose peroxidase is eluted into six fractions, differing in their electrophoretic properties. The enzyme showed optimal activity at pH 4.1-5.0, when the enzyme fractions of guaiacol adsorbed on DEAE-cellulose were used as a substrate; in case of enzyme fractions adsorbed on CM-cellulose it was observed within pH range of 5.4-6.2. The dependence curves of the initial rate of the reaction on the substrate concentration were S-shaped in case of the latter fractions. Peroxidase is shown to catalyze the oxidation of tea catechins; its activity is inhibited by the products of their condensation. The catalytic effect of the enzyme on the oxidation of phenolic acids, e.g. chlorogenic, caffeic and gallic, was far stronger than on that of tea catechins, pyrogallol and pyrocatechin. It was established that two fractions of the enzyme possess predominantly the phloroglucinol oxidase activity, whereas the other fractions do not catalyze the oxidation of phloroglucin. The molecular weights of some peroxidase fractions estimated by polyacryl amide gel electrophoresis are 26.000+/-1.100, 45.00+/-1.200 and 50.000+/-1.500.

Catechin↗
PubMed2005

[Synthesis of 2,3,4-trihydroxyacetophenone hydrazones and study on their spectral properties].

2,3,4-Trihydroxyacetophenone was synthesized with pyrogallol. Benzoylhydrazone and p-hydroxybenzoylhydrazone were synthesized using the reaction of ethyl benzoate and methyl p-hydroxybenzoate with hydrazine hydrate. Three novel 2,3,4-trihydroxyacetophenone hydrazones were synthesized using the reaction of 2,3,4-trihydroxyacetophenone with benzoylhydrazone, p-hydroxybenzoylhydrazone and phenylhydrazine. IR, UV and the fluorescence spectrum of 2,3,4-trihydroxyacetophenone hydrazones were studied.

Acetophenones↗
PubMedDate not supplied

Comparative study of superoxide dismutase activity assays in Crocus sativus L. corms.

Superoxide dismutase catalyzes the breakdown of the superoxide radical anion and provides the first line of defense against oxygen toxicity. Its vital importance has made it the subject of numerous investigations. Several assays have been proposed for the detection and quantitation of superoxide dismutase activity, but their use has remained controversial and no comparative studies have been reported. In this investigation, three commonly used methods were compared for the measurement of superoxide dismutase activity in Crocus sativus L. corm extract. The methods, based on a competition between the enzyme itself and another superoxide scavenger, involved respectively cytochrome c reduction, nitro blue tetrazolium reduction, and pyrogallol autoxidation. Because of its accuracy, reproducibility, simplicity and cost benefit, the latter method was the most appropriate.

Crocus↗
PubMed1991

Effect of gamma irradiation on alpha-tocopherol levels in ruminant blood samples.

Quantification of circulating levels of vitamin E in free-ranging species can provide useful guidelines for evaluating nutrient status in captive exotic animals. Under current USDA regulations, ruminant plasma or serum samples must be subjected to 1) live-animal testing and viral screening, or 2) gamma (gamma-) irradiation prior to importation. Because irradiation is known to promote free radical formation and destruction of alpha-tocopherol in various tissues, these studies were conducted to evaluate the effect of irradiation on ruminant blood fractions with and without added antioxidant. alpha-tocopherol levels were measured in paired (irradiated vs. unirradiated) plasma or serum samples collected from zoo ruminants (n = 8 spp.). Irradiation caused highly significant (P less than 0.001) but inconsistent destruction of alpha-tocopherol. Addition of 10% volume of a 1% pyrogallol solution to plasma or serum protected against alpha-tocopherol deterioration during gamma-irradiation. In order to ensure valid comparative values for vitamin E studies while complying with USDA regulations, it is recommended that plasma or serum samples collected from ruminants outside the US be treated with antioxidant prior to importation.

Animals↗
PubMed1989

Possible involvement of 5-lipoxygenase products in the generation of endothelium-derived relaxing factor.

Acetylcholine and substance P applied to the donor tissue, dog femoral artery segments with endothelium, produced moderate relaxations of the assay tissue, endothelium-denuded dog coronary artery strips. The relaxation was attenuated markedly by treatment of the assay tissue with hydroquinone and abolished by oxyhemoglobin or methylene blue. In this bioassay system, the effect of AA861 and TMK777, new 5-lipoxygenase inhibitors, was evaluated. When the donor tissue was treated with AA861 or TMK777, the responses to acetylcholine and substance P were attenuated moderately, whereas the relaxation by nitroglycerin was not influenced by AA861. However, the inhibitors when infused just below the donor tissue did not attenuate relaxant responses to acetylcholine and substance P. Application of superoxide dismutase (SOD) to the donor tissue caused a relaxation of the assay tissue, and potentiated the relaxation by acetylcholine and substance P. AA861 and TMK777 suppressed the relaxant responses to acetylcholine and substance P, respectively, in the presence and absence of SOD to a similar extent and abolished the SOD-induced relaxation. Pyrogallol abolished the relaxation by acetylcholine, but did not inhibit the response when the donor tissue was pretreated with SOD. Therefore, it appears that AA861 and TMK777 do not degrade endothelium-derived relaxing factor (EDRF) in the perfusate via generation of superoxide anion or block the action of EDRF on vascular smooth muscle, but interfere with the synthesis and/or release of EDRF. The findings obtained so far support the idea that lipoxygenase products participate in the generation of EDRF.

Acetylcholine↗
PubMed1975

[Biphasic (ulcer-forming and ulcer-preventing) effect of adrenaline in rats].

Adrenaline-induced gastric ulceration was studied in rats. Adrenaline in high doses caused gastric ulcer, which was completely blocked by pretreatment with alpha-blockers (phenoxybenzamine, dibenamine), but not by pretreatment with propranolol or atropine, nor by vagotomy, hypophysectomy or adrenalectomy. After successive administration of adrenaline, once daily for 7 days, however, no gastric ulcer was observed. Recovery from the ulcerogenic action of adrenaline was seen after 4 weeks withdrawal. Pretreatment with a small dose of adrenaline inhibited the ulcerogenic action of a high dose of adrenaline. Pretreatment with reserpine, pyrogallol or iproniazid inhibited the action of adrenaline. It is concluded that adrenaline has a biphasic effect on gastric ulceration, the ulcerogenic action is due to its alpha-action and antiulcerogenic effect is due to development of tachyphylaxis.

Adrenalectomy↗
PubMed1988

High efficiency coupling of alpha-1 adrenergic receptors to inositol phospholipid metabolism revealed by denervation of rat vas deferens.

The effect of surgical denervation on alpha-1 adrenergic receptor-stimulated inositol phosphate (IP) formation was examined in rat vas deferens. Rings of tissue from acutely reserpinized animals were incubated with [3H]inositol in the presence of lithium to block IP degradation and desmethylimipramine to block neuronal uptake of norepinephrine. Eighteen days after denervation the potency of norepinephrine in stimulating [3H]IP accumulation was increased 10-fold. The potency of epinephrine was increased only 3.5-fold, and the potency of phenylephrine was not altered significantly. The potency of norepinephrine in control tissues incubated with 0.1 microM desmethylimipramine was unaffected by addition of cocaine to further block neuronal uptake; however, addition of pyrogallol and pargyline to block metabolic degradation increased the potency of norepinephrine in these tissues by 6-fold. Two days after denervation there was a similar 5-fold increase in the potency of norepinephrine. In denervated tissues, the potency of norepinephrine in stimulating [3H]IP accumulation was decreased about 40-fold after receptor inactivation with 1 microM phenoxybenzamine. These results suggest that there is a substantial alpha-1 adrenergic receptor reserve for stimulating [3H]IP accumulation in rat vas deferens which is normally obscured by rapid inactivation of norepinephrine. The increase in the potency of norepinephrine after denervation appears to be due to removal of these inactivation mechanisms.

Animals↗
PubMed1985

Comparative study of mechanical responses of hepatic arteries strips to adrenalin in presence of pyridoxine and pyridoxal-5'-phosphate.

Since it is known that PLP inhibits "in vitro" the COMT much more than pyridoxine; the influence of pyridoxine to the response of hepatic arteries isolated to AD has been compared to the influence of PLP to the same arteries. As for as the increase in percent is concerned, the result is that PLP gives rise to a greater answer to AD than pyridoxine. Such effects lacked when pyrogallol, a powerful COMT inhibitor, was present. Taking such results as a basis, it has been concluded that the mechanism of action of pyridoxine and of PLP was metabolic and that it was based on the COMT inhibition, even for the hepatic arteries. It was been also deduced that the higher efficiency of PLP compared to the pyridoxine's was due to its greater capacity to inhibit the COMT.

Animals↗
PubMed1973

Spectrophotometric method for determination of tocopherol in red blood cells.

A relatively rapid procedure is described for the spectrophotometric determination of total tocopherol in red blood cells (RBC) based on a modification of the original Emmerie-Engel reaction. The critical feature in this method is the presence of a large amount of an added antioxidant, pyrogallol or ascorbic acid, during the saponification and extraction stages and the use of thin-layer chromatography for tocopherol purification. The total tocopherol levels of plasma and erythrocytes were determined for a number of human subjects, for patients with abetalipoproteinemia, and for rats. It was found that these levels had a wide range in normal human subjects but that the ratio of RBC to plasma tocopherol was relatively constant and equal to 0.18, uncorrected, and 0.21 when both RBC and plasma values were corrected to 100% recovery. The RBC-to-plasma ratio for rats was 0.39. The accuracy of this ratio determined by the spectrophotometric procedure was verified by measuring the distribution of [(14)C]tocopherol in RBC and plasma when radioactive vitamin E was introduced into the blood by both in vitro and in vivo techniques. The addition of radioactive tocopherol to RBC or plasma at the initial stage of the analysis permits an accurate determination of the total tocopherol in RBC or plasma by calculations based on the recovery of the added isotope. This procedure for erythrocyte tocopherol analysis is compared with a gas-liquid chromatographic method in current use.

Abetalipoproteinemia↗
PubMed1971

Mechanism of potentiation of contractor responses to catecholamines by methylxanthines in aortic strips.

1. Caffeine and theophylline increased the amplitude of contractor esponses of untreated and reserpine pretreated rabbit aortic strips to catecholamines (adrenaline, alpha-methylnoradrenaline, noradrenaline). Responses to amines without both the 3- and 4-OH groups in the benzene ring (methoxamine, phenylephrine, Synephrine) were not increased by theophylline and only those to Synephrine were slightly enhanced by caffeine.2. Compounds which inhibit catechol-O-methyltransferase (pyrogallol, tropolone, U-0521) potentiated responses to catecholamines and abolished the enhancing effect of theophylline and caffeine. Also, the potentiation produced by inhibitors of O-methylation was significantly reduced in the presence of the methylxanthines.3. Experiments done with the aid of the technique of oil immersion, to eliminate the diffusion of drug from the tissue into the bathing medium, showed that theophylline and caffeine decreased the rate of inactivation of adrenaline by O-methylation.4. These findings indicate that methylxanthines potentiate the contractor responses to catecholamines in aortic strips by inhibiting their extraneuronal inactivation.

Animals↗
PubMed1983

Liquid-chromatographic determination of alpha- and gamma-tocopherols in erythrocytes, with fluorescence detection.

We have adapted to erythrocytes a method for the determination of alpha- and gamma-tocopherols in plasma and platelets. Erythrocytes (50 microL) were extracted with methanol containing tocol (internal standard) and pyrogallol. Tocopherols were partitioned into chloroform, washed, and injected in methanol onto a reversed-phase (C18) "high-performance" liquid-chromatographic column. The mobile phase was methanol/water (99/1 by vol) at a flow rate of 2 mL/min and detection was with a "high-performance" spectrophotofluorometer. The limit of detection for either tocopherol is 0.10 microgram/mL of packed cells. Analytical recoveries ranged from 93 to 104%. Some values for tocopherols in human erythrocytes are presented.

Blood Platelets↗
PubMed1978

Sensitization to the generalized Shwartzman reaction by catechol-O-methyltransferase inhibitors.

The generalized Shwartzman reaction (GSR) was produced by a single injection of endotoxin in male rats pretreated with catechol-o-methyltransferase (COMT) inhibitors (tropolone, pyrogallol). Such a result was not obtained with inhibitors (pargyline, phenelzine, isocarboxazide) of the monoamine oxidase (MAO). The inhibitors of the COMT were found to enhance the action of endotoxin on the coagulation system such as evidenced by the increased consumptions of Hageman factor, fibrinogen, and platelets. Tropolone-treated rabbits did not require exogenous stimulation of alpha-adrenergic receptor sites by norepinephrine to localize thrombi in the glomerular capillaries when Hageman factor was activated by ellagic acid and fibrinolysis inhibited by epsilon-amino-caproic acid. It is concluded that interference with the degradation of circulating catecholamines results in sensitization to the generalized Shwartzman reaction.

Animals↗