INDUCTION OF DDT-METABOLIZING ENZYMES IN MICROSOMES OF RAT LIVER AFTER ADMINISTRATION OF DDT

1965 ◽  
Vol 43 (8) ◽  
pp. 1289-1293 ◽  
Author(s):  
Antonio Morello
Keyword(s):  
Phenolic Compound ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Enzyme Synthesis ◽  
Rat Liver Microsomes ◽  
Metabolizing Enzymes ◽  
Mammalian Liver

DDT is metabolized by rat liver microsomes to a phenolic compound and to a reduced derivative similar to DDD. When rats were injected intraperitoneally with DDT, the microsomal DDT-metabolizing activity was greatly increased. This effect was blocked by the administration of puromycin. DDT administration also increases the content of liver microsomal protein. The results show that the insecticide probably increases the DDT-metabolizing activity of mammalian liver by inducing enzyme synthesis.

The Effect of Dietary Sulfur-Containing Amino Acids on the Activity of Drug-Metabolizing Enzymes in Rat-Liver Microsomes

1979 ◽  
Vol 109 (5) ◽  
pp. 864-871 ◽  
Author(s):  
Jacques Magdalou ◽  
Daniele Steimetz ◽  
Anne-Marie Batt ◽  
Bernard Poullain ◽  
Gérard Siest ◽  
...  
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Drug Metabolizing Enzymes ◽  
Rat Liver Microsomes ◽  
Metabolizing Enzymes ◽  
Sulfur Containing

Properties of a dolichol phosphokinase activity associated with rat liver microsomes

1980 ◽  
Vol 58 (10) ◽  
pp. 1051-1056 ◽  
Author(s):  
Jack W. Rip ◽  
Kenneth K. Carroll
Keyword(s):  
Rat Liver ◽  
Metal Ion ◽  
Reaction Rate ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Optimum Concentration ◽  
Nucleoside Triphosphate ◽  
Rat Liver Microsomes ◽  
Detergent Concentration ◽  
Dolichyl Phosphate

Rat liver microsomes show a capacity to synthesize [1-3H]dolichyl phosphate from [1-3H]-dolichol. Formation of [1-3H]dolichyl phosphate increased continuously over 15 min although the reaction rate was never completely linear. Product formation was directly proportional to microsomal protein concentration between 1.1 mg/mL and the highest concentration tested, 5.5 mg/mL. The reaction rate was linear with respect to the dolichol content of the assay mixture to a saturation point (120 μM). An apparent Km of 50 μM was established for dolichol. The normal phosphate donor for the reaction is CTP and not ATP. The optimum concentration of CTP was 10 mM, and an apparent Km of 4 mM was calculated for this nucleoside triphosphate. The reaction was totally dependent on divalent metal ion, magnesium being more effective than calcium. The optimum concentration of magnesium ion and CTP were the same (10 mM), suggesting that MgCTP2− is utilized as the normal enzyme substrate. Activity measured in the absence of Triton X-100 was only 5% of the activity observed at the optimum (0.5% w/v) detergent concentration. The measurable levels of dolichol phosphokinase could be doubled by the inclusion of 10–15 mM NaF as phosphatase inhibitor. Optimal enzymatic activity was obtained between pH 7.0 and pH 7.5 and could be inhibited by EDTA. The sulfhydryl reagent DTT was slightly stimulatory while the product of the reaction, dolichyl phosphate, was noninhibitory at the highest concentration tested (13.8 μM). The second reaction product (CDP) inhibits the enzymatic phosphorylation of dolichol.

Effect of natural and structurally modified bile acids on cholesterol metabolizing enzymes in rat liver microsomes

1989 ◽  
Vol 51 (2) ◽  
pp. 119-126 ◽  
Author(s):  
M. Crestani ◽  
E. De Fabiani ◽  
B. Malavasi ◽  
M. Cancellieri ◽  
G. Galli ◽  
...  
Keyword(s):  
Bile Acids ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Metabolizing Enzymes

scholarly journals Microsomal formation of S-nitrosoglutathione from organic nitrites: possible role of membrane-bound glutathione transferase

1996 ◽  
Vol 313 (2) ◽  
pp. 377-380 ◽  
Author(s):  
Yanbin JI ◽  
Theodorus P. M. AKERBOOM ◽  
Helmut SIES
Keyword(s):  
Rat Liver ◽  
Glutathione Transferase ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Rat Liver Microsomes ◽  
Glutathione S Transferase ◽  
Alkyl Nitrites ◽  
Amyl Nitrite ◽  
Membrane Bound ◽  
Gst Activity

The formation of S-nitrosoglutathione (GSNO) from amyl nitrite and n-butyl nitrite was studied in rat liver microsomes, employingN-ethylmaleimide (MalNEt) as an activator and indomethacin as an inhibitor of microsomal glutathione S-transferase (GST). Rates were compared with GST activity measured with 1-chloro-2,4-dinitrobenzene(CDNB) as a substrate. MalNEt stimulated GST activity and the formation of GSNO from amyl nitrite and n-butyl nitrite about 10-fold. Increasing concentrations of indomethacin inhibited both reactions in parallel. N-Acetyl-L-cysteine but not L-cysteine could substitute for GSH. It is concluded that rat liver microsomal GST catalyses the formation of GSNO from amyl nitrite and n-butyl nitrite. The activity of the MalNEt-stimulated microsomal GST is calculated to be about 17 units/mg of enzyme with the alkyl nitrites and about 16 units/mg of enzyme with CDNB as a substrate, assuming that 3% of microsomal protein is GST. These rates are comparable with those obtained for cytosolic GSTs. Thus microsomal GST may play a significant role in the metabolism of alkyl nitrites in biological membranes.

scholarly journals Inhibition of UGT2B7 Enzyme Activity in Human and Rat Liver Microsomes by Herbal Constituents

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2696 ◽  
Author(s):  
Nurul Abdullah ◽  
Sabariah Ismail
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Herbal Medicines ◽  
Inhibitory Effect ◽  
Intrinsic Clearance ◽  
Rat Liver Microsomes ◽  
Metabolizing Enzymes ◽  
Conventional Drug ◽  
Ic50 Values

The co-use of conventional drug and herbal medicines may lead to herb-drug interaction via modulation of drug-metabolizing enzymes (DMEs) by herbal constituents. UDP-glucuronosyltransferases (UGTs) catalyzing glucuronidation are the major metabolic enzymes of Phase II DMEs. The in vitro inhibitory effect of several herbal constituents on one of the most important UGT isoforms, UGT2B7, in human liver microsomes (HLM) and rat liver microsomes (RLM) was investigated. Zidovudine (ZDV) was used as the probe substrate to determine UGT2B7 activity. The intrinsic clearance (Vmax/Km) of ZDV in HLM is 1.65 µL/mg/min which is ten times greater than in RLM, which is 0.16 µL/mg/min. Andrographolide, kaempferol-3-rutinoside, mitragynine and zerumbone inhibited ZDV glucuronidation in HLM with IC50 values of 6.18 ± 1.27, 18.56 ± 8.62, 8.11 ± 4.48 and 4.57 ± 0.23 µM, respectively, hence, herb-drug interactions are possible if andrographolide, kaempferol-3-rutinoside, mitragynine and zerumbone are taken together with drugs that are highly metabolized by UGT2B7. Meanwhile, only mitragynine and zerumbone inhibited ZDV glucuronidation in RLM with IC50 values of 51.20 ± 5.95 μM and 8.14 ± 2.12 µM, respectively, indicating a difference between the human and rat microsomal model so caution must be exercised when extrapolating inhibitory metabolic data from rats to humans.

Dolichol and polyprenol kinase activities in microsomes from etiolated rye seedlings

1992 ◽  
Vol 70 (6) ◽  
pp. 455-459 ◽  
Author(s):  
Robert T. Rymerson ◽  
Kenneth K. Carroll ◽  
Jack W. Rip
Keyword(s):  
Rat Liver ◽  
Divalent Cations ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Rat Liver Microsomes ◽  
Ph Optimum ◽  
Dolichyl Phosphate ◽  
Triton X ◽  
Enhance Activity ◽  
Better Than

Dolichol kinase activity in microsomes from etiolated rye seedlings had a pH optimum at 8 with a shoulder at pH 6.5. Triton X-100 (0.4%) was required for optimum activity. Exogenous divalent cations did not enhance activity, although Mg+2 was added routinely. Rye microsomes were found to contain dolichol and polyprenol in a ratio of 3 to 2. Rye, soybean embryo, and rat liver microsomes catalyzed the synthesis of 78, 52, and 516 nmol [14C]dolichyl phosphate/(mg microsomal protein∙h) compared with 21, 22, and 49 nmol [3H]polyprenyl phosphate/(mg microsomal protein∙h), respectively. It is clear that microsomes from plant systems can catalyze the phosphorylation of polyprenol better than rat liver when compared with their abilities to catalyze the phosphorylation of dolichol. It is not known whether one or more kinases is responsible for catalyzing the phosphorylation of these two closely related groups of compounds.Key words: dolichol, polyprenol, dolichyl phosphate, polyprenyl phosphate, kinases.

scholarly journals Effect of pituitary hormones on carboxylesterase and drug metabolizing enzymes in rat liver microsomes

1984 ◽  
Vol 36 ◽  
pp. 73
Author(s):  
Masakiyo Hosokawa ◽  
Kenji Hattori ◽  
Mayumi Igarashi ◽  
Tetsuo Satoh ◽  
Satoshi Ohkawara ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Pituitary Hormones ◽  
Drug Metabolizing Enzymes ◽  
Rat Liver Microsomes ◽  
Metabolizing Enzymes
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