scholarly journals The cytochromes in microsomal fractions of germinating mung beans

1981 ◽  
Vol 194 (3) ◽  
pp. 743-751 ◽  
Author(s):  
G A F Hendry ◽  
J D Houghton ◽  
O T G Jones
Keyword(s):  
Cytochrome B ◽  
Mung Bean ◽  
Microsomal Fraction ◽  
Degradation Mechanism ◽  
Cytochrome B5 ◽  
Rapid Degradation ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Detailed studies of microsomal cytochromes from mung-bean radicles showed the presence of cytochrome P-420, particularly in dark-grown seedlings, accompanied by smaller quantities of cytochrome P-450. Similar proportions of cytochrome P-420 to cytochrome P-450 were found spectrophotometrically in vivo with whole radicles and hypocotyls. Assayed in vitro, maximum concentrations of both cytochromes were attained after 4 days of growth, before undergoing rapid degradation. Illumination of seedlings stabilized cytochrome P-450 and decreased the amount of cytochrome P-420. Three b cytochromes were present in the microsomal fraction, namely cytochromes b-562.5 (Em + 105 +/- 23 mV), b-560.5 (Em + 49 +/- 13 mV) and b5 (Em - 45 +/- 14 mV), all at pH 7.0. Of the b cytochromes, cytochrome b5 alone undergoes a rapid degradation after day 4, Changes in cytochrome b concentrations were confined to the microsomal fraction: mitochondrial b cytochrome concentrations were unaltered with age. Protohaem degradation (of exogenous methaemalbumin) was detected in microsomal fractions of mung beans. The rates of degradation were highest in extracts of young tissue and declined after day 4. The degradation mechanism and products did not resemble those of mammalian haem oxygenase.

scholarly journals Phenylhydrazine-mediated induction of haem oxygenase activity in rat liver and kidney and development of hyperbilirubinaemia. Inhibition by zinc-protoporphyrin

1984 ◽  
Vol 217 (2) ◽  
pp. 409-417 ◽  
Author(s):  
M D Maines ◽  
J C Veltman
Keyword(s):  
Rat Liver ◽  
Zinc Protoporphyrin ◽  
Serum Total Bilirubin ◽  
Potent Inducer ◽  
Oxygenase Activity ◽  
Liver And Kidney ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Phenylhydrazine was found to be a potent inducer of microsomal haem oxygenase activity in rat liver and kidney, but not in spleen. The phenylhydrazine-mediated increase in haem oxygenase activity was time-dependent. Maximum activity was attained 12h after treatment in the liver, and 24h after treatment in the kidney. The increases in the activity of haem oxygenase in the liver and the kidney could be inhibited by cycloheximide. Furthermore, the increases could not be elicited by the treatment of microsomal preparations in vitro with phenylhydrazine. In consonance with the increased haem oxygenase activity, a marked increase (16-fold) was observed in the serum total bilirubin concentration in phenylhydrazine-treated rats. The mechanism of haem degradation promoted by phenylhydrazine in vivo appears to differ from that in vitro; only in the former case is bilirubin formed as the end-product of haem degradation. When rats were given zinc-protoporphyrin (40 mumol/kg) 12h before and after phenylhydrazine treatment, the phenylhydrazine-mediated increases in haem oxygenase activity in the liver and the kidney were effectively blocked. Treatment of rats in vivo with the metalloporphyrin also inhibited the activity of splenic haem oxygenase, and promoted a major decrease in the serum bilirubin levels. In phenylhydrazine-treated animals, the microsomal content of cytochrome P-450 was significantly decreased in the absence of a decrease in the microsomal haem concentration. The decrease in cytochrome P-450 content was accompanied by an increased absorption in the 420nm region of the reduced CO-difference spectrum, suggesting the conversion of the cytochrome to an inactive form. The marked depletion of cellular glutathione levels suggests that this conversion may be related to the action of active intermediates and free radicals formed in the course of the interaction of phenylhydrazine with the haem moiety of cytochrome P-450.

scholarly journals Degradation of cytochrome P-450 haem by carbon tetrachloride and 2-allyl-2-isopropylacetamide in rat liver in vivo and in vitro. Involvement of non-carbon monoxide-forming mechanisms

1979 ◽  
Vol 184 (3) ◽  
pp. 481-489 ◽  
Author(s):  
Philip S. Guzelian ◽  
Robert W. Swisher
Keyword(s):  
Lipid Peroxidation ◽  
Free Radicals ◽  
Carbon Tetrachloride ◽  
Pulse Labelling ◽  
Forming Mechanism ◽  
Oxygenase Activity ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Degradation of intrinsic hepatic [14C]haem was analysed as 14CO formation in living rats and in hepatic microsomal fractions prepared from these animals 16h after pulse-labelling with 5-amino[5-14C]laevulinic acid, a precursor that labels bridge carbons of haem in non-erythroid tissues. NADPH-catalysed peroxidation of microsomal lipids in vitro (measured as malondialdehyde) was accompanied by loss of cytochrome P-450 and microsome-associated [14C]haem (largely cytochrome P-450 haem), but little 14CO formation. No additional 14CO was formed when carbon tetrachloride and 2-allyl-2-isopropylacetamide were added to stimulate lipid peroxidation and increase loss of cytochrome P-450 [14C]haem. Because the latter effect persisted despite inhibition of lipid peroxidation with MnCl2 or phenyl-t-butylnitrone(a spin-trapping agent for free radicals), it was concluded that carbon tetrachloride, as reported for 2-allyl-2-isopropylacetamide, may promote loss of cytochrome P-450 haem through a non-CO-forming mechanism independent of lipid peroxidation. By comparison with breakdown of intrinsic haem, catabolism of [14C]methaemalbumin by microsomal haem oxygenase in vitro produced equimolar quantities of 14CO and bilirubin, although these catabolites reflected only 18% of the degraded [14C]haem. This value was increased to 100% by addition of MnCl2, which suggests that lipid peroxidation may be involved in degradation of exogenous haem to products other than CO. Phenyl-t-butylnitrone completely blocked haem oxygenase activity, which suggests that hydroxy free radicals may represent a species of active oxygen used by this enzyme system. After administration of carbon tetrachloride or 2-allyl-2-isopropylacetamide to labelled rats, hepatic [14C]haem was decreased and haem oxygenase activity was unchanged; however, 14CO excretion was either unchanged (carbon tetrachloride) or decreased (2-allyl-2-isopropylacetamide). These changes were unaffected by cycloheximide pretreatment. From the lack of parallel losses of cytochrome P-450 [14C]haem and 14CO excretion, one may infer that an important fraction of hepatic [14C]haem in normal rats is degraded by endogenous pathways not involving CO. We conclude that carbon tetrachloride and 2-allyl-2-isopropylacetamide accelerate catabolism of cytochrome P-450 haem through mechanisms that do not yield CO as an end product, and that are insensitive to cycloheximide and independent of haem oxygenase activity.

The protective properties of synthetic porphyrin tin complexes in toxic hyperbilirubinemia

2000 ◽  
Vol 04 (03) ◽  
pp. 243-247 ◽  
Author(s):  
T. O. PHILIPPOVA ◽  
B. N. GALKIN ◽  
N. YA. GOLOVENKO ◽  
Z. I. ZHILINA ◽  
S. V. VODZINSKII
Keyword(s):  
Heme Oxygenase ◽  
Serum Bilirubin ◽  
Protoporphyrin Ix ◽  
Serum Bilirubin Level ◽  
Oxygenase Activity ◽  
Tetraphenyl Porphyrin ◽  
Tin Complexes ◽  
Cytochrome P 450

Tin complexes of meso-substituted synthetic porphyrins, namely Sn 4+-meso-tetraphenyl- porphyrin ( Sn - TPP ) and Sn 4+-meso-tetrakis(N-methyl-3-pyridyl)porphyrin tetratosylate ( Sn - TMe -3- PyP ), efficiently decrease the serum bilirubin level when injected subcutaneously at a dose of 100 μM kg−1 body weight into mice. These compounds are active during hyperbilirubinemia, induced by phenylhydrazine, hemin and tetrachloromethane, and also during autoimmune hemolytic anemia. In the latter case a decrease in serum bilirubin content was observed, as well as a decrease in the amount of blood reticulocytes which reflects a milder course of the disease. The Sn complexes under study induce, in vivo, cytochrome P-450, inhibit microsomal heme oxygenase and decrease the intensity of lipid peroxidation. At the same time, in vitro the hepatic and splenic heme oxygenase activity is blocked only when a 0.1 μM concentration of Sn - TMe -3- PyP or Sn -protoporphyrin IX is added to the incubation mixture. Sn - TPP does not affect the activity of this enzyme in vitro.

Influence of Safeners on the in vivo and in vitro Metabolism of Bentazon and Metolachlor by Grain Sorghum Shoots: a Preliminary Report

1991 ◽  
Vol 46 (9-10) ◽  
pp. 906-914 ◽  
Author(s):  
Donald E. Moreland ◽  
Frederick T. Corbin
Keyword(s):  
Grain Sorghum ◽  
In Vitro Studies ◽  
Naphthalic Anhydride ◽  
Surface Sterilization ◽  
Polar Components ◽  
In Vitro Shoots ◽  
Treated Seed ◽  
Cytochrome P 450

Abstract Metabolism of bentazon and metolachlor by excised shoots and a microsomal fraction iso­lated from the shoots, of 3-day-old, dark-grown, grain sorghum (Sorghum bicolor cv. Funk G 522 DR) seedlings was studied. The effects of seed treatments, on the subsequent metabo­lism of the herbicides, with the safeners naphthalic anhydride, oxabetrinil, and CGA 133205 were compared against surface-sterilization and Captan-treatments. Bentazon was aryl hydroxylated in both in vivo and in vitro studies with the hydroxylated derivative undergoing glycosylation only under in vivo conditions. Both shoots and microsomes isolated from shoots of safener-treated seed showed enhanced metabolism of bentazon relative to the controls. In­ hibition by tetcyclacis, a potent inhibitor of plant cytochrome P-450 monooxygenases, in both the in vivo and in vitro studies, and a requirement for NADPH in the in vitro studies suggested that the formation of hydroxybentazon was mediated by a cytochrome P-450 monooxygenase. Metolachlor was metabolized to polar material and O-desmethylmetolachlor under in vivo conditions. Only the demethylated product was formed in vitro. Shoots isolated from safener-treated seed showed enhanced formation of polar com pounds which were assumed to have arisen from conjugation with glutathione. Tetcyclacis did not affect the formation of the polar components. However, the formation of O-desmethylmetolachlor was depressed in the shoots excised from safener-treated seed under both in vivo and in vitro conditions. Tetcyclacis completely prevented formation of the demethylated metabolite. Hence, formation of this meta­bolite is considered to be P-450 mediated. The differential response obtained with the safeners, i.e., stimulation of aryl hydroxylation of bentazon and depression of metolachlor demethylation, suggests that the reactions are probably catalyzed by different cytochrome P-450 mono­oxygenases.

Biosynthesis of Nitrogenous Phospholipids in Spinach Leaves

1974 ◽  
Vol 52 (6) ◽  
pp. 469-482 ◽  
Author(s):  
M. O. Marshall ◽  
M. Kates
Keyword(s):  
Microsomal Fraction ◽  
Enzyme System ◽  
Supernatant Fraction ◽  
Exchange Reactions ◽  
Methylation Pathway ◽  
Ethanolamine Kinase ◽  
Spinach Leaves

Pathways for biosynthesis of phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), in spinach leaves have been studied both in vivo (whole leaves and leaf slices) and in vitro (cell-free leaf fractions). Biosynthesis of PS was shown to occur by the action of a particle-bound CDP-diglyceride: serine phosphatidyltransferase, and PE by the action of a PS-decarboxylase localized in the 100 000 × g supernatant fraction. PE was also formed by the operation of the CDP-ethanolamine:diglyceride phosphorylethanolamine transferase, localized in the microsomal fraction. The presence of ethanolamine kinase required for formation of phosphorylethanolamine was demonstrated in vitro, but not the presence of CTP:phosphorylethanolamine cytidyltransferase; however, the latter is presumed present on the basis of in vivo results. Operation of the methylation pathway for biosynthesis of PC was established in vivo, and direct methylation of phosphatidyl-N-methylethanolamine to phosphatidyl-N,N-dimethylethanolamine (PE-diMe) and of PE-diME to PC by S-adenosylmethionine was demonstrated with a particulate enzyme system localized in the microsomal fraction; direct methylation of PE itself could not be shown in this system. PC was also synthesized by the CDP-choline:diglyceride phosphorylcholine transferase system localized in the microsomal fraction. Synthesis of PE and PC by Ca2+-stimulated exchange reactions with ethanolamine and choline, respectively, could be demonstrated, but at low rates. However, no synthesis of PS by exchange reactions with serine could be detected.

scholarly journals Phenobarbital influence on neuromuscular block produced by rocuronium in rats

2008 ◽  
Vol 23 (4) ◽  
pp. 343-347 ◽  
Author(s):  
Angélica de Fátima de Assunção Braga ◽  
Caroline Coutinho de Barcelos ◽  
Franklin Sarmento da Silva Braga ◽  
Samanta Cristina Antoniassi Fernandes ◽  
Yoko Oshima Franco ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Neuromuscular Blockade ◽  
Neuromuscular Block ◽  
Cytochrome B5 ◽  
Muscle Response ◽  
In Vivo Experiments ◽  
Hepatic Microsomes ◽  
Enzymatic Induction

PURPOSE: To evaluate in vitro and in vivo neuromuscular blockade produced by rocuronium in rats treated with Phenobarbital and to determine cytochrome P450 and cytochrome b5 concentrations in hepatic microsomes. METHODS: Thirty rats were included in the study and distributed into 6 groups of 5 animals each. Rats were treated for seven days with phenobarbital (20 mg/kg) and the following parameters were evaluated: 1) the amplitude of muscle response in the preparation of rats exposed to phenobarbital; 2) rocuronium effect on rat preparation exposed or not to phenobarbital; 3) concentrations of cytochrome P450 and cytochrome b5 in hepatic microsomes isolated from rats exposed or not to phenobarbital. The concentration and dose of rocuronium used in vitro and in vivo experiments were 4 µg/mL and 0,6 mg/kg, respectively. RESULTS: Phenobarbital in vitro and in vivo did not alter the amplitude of muscle response. The neuromuscular blockade in vitro produced by rocuronium was significantly different (p=0.019) between exposed (20%) and not exposed (60%) rats; the blockade in vivo was significantly greater (p=0.0081) in treated rats (93.4%). The enzymatic concentrations were significantly greater in rats exposed to phenobarbital. CONCLUSIONS: Phenobarbital alone did not compromise neuromuscular transmission. It produced enzymatic induction, and neuromuscular blockade in vivo produced by rocuronium was potentiated by phenobarbital.

Identification of human cytochrome P 450 s that metabolise anti-parasitic drugs and predictions of in vivo drug hepatic clearance from in vitro data

2003 ◽  
Vol 59 (5-6) ◽  
pp. 429-442 ◽  
Author(s):  
Xue-Qing Li ◽  
Anders Bj�rkman ◽  
Tommy B. Andersson ◽  
Lars L. Gustafsson ◽  
Collen M. Masimirembwa
Keyword(s):  
Hepatic Clearance ◽  
Human Cytochrome ◽  
Cytochrome P 450 ◽  
Vitro Data ◽  
In Vitro Data

Alterations of Hepatic Microsomal Drug Metabolism by Glucagon

1975 ◽  
Vol 53 (5) ◽  
pp. 873-879 ◽  
Author(s):  
Jacob V. Aranda ◽  
Kenneth W. Renton
Keyword(s):  
Substrate Oxidation ◽  
Type I ◽  
Nadph Cytochrome ◽  
Transport Chain ◽  
Hexobarbital Sleeping Time ◽  
Nadph Oxidation ◽  
In Vivo Effects ◽  
Cytochrome P 450

The effect of glucagon on the components of the hepatic microsomal electron transport chain (NADPH oxidase, NADPH cytochrome c reductase (EC 1.6.2.4), cytochrome P-450, and NADPH cytochrome P-450 reductase), and on two representative oxidative pathways (aminopyrine N-demethylation, a type I substrate oxidation; and aniline p-hydroxylation, a type II substrate oxidation) was determined. Microsomes from rats pretreated with glucagon (300 μg/kg per day for 3 days) showed a significant decrease in NADPH oxidation and in aminopyrine N-demethylation with a prolonged hexobarbital sleeping time, and a significant increase in aniline p-hydroxylation. Microsomes from rats pretreated with a lower dose of glucagon (30 μg/kg per day for 3 days) showed a significant decrease in the microsomal N-demethylation of aminopyrine. Glucagon had no effect when added in vitro to microsomes, suggesting that the in vivo effects of glucagon are mediated indirectly in the intact animal.

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