Regulation of selectivity of CDPcholine: 1,2-diacyl-sn-glycerol cholinephosphotransferase in rat liver microsomes towards different molecular species of 1,2-diacyl-sn -glycerols

1977 ◽  
Vol 55 (7) ◽  
pp. 700-705 ◽  
Author(s):  
B. J. Holub
Keyword(s):  
Rat Liver ◽  
Molecular Species ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Physiological Conditions ◽  
Phosphatidylcholine Biosynthesis ◽  
Significant Difference ◽  
Phosphatidylcholine Synthesis

The suitability of monoenoic, dienoic, tetraenoic, and hexaenoic molecular species of 1,2-diacyl-sn-glycerols as substrates for the CDPcholine: 1,2-diacyl-sn-glycerol cholinephosphotransferase (EC 2.7.8.2) was studied in rat liver microsomes. No statistically significant difference in the rates of phosphatidylcholine synthesis with the various diacylglycerols was found at 0.40 mM, although a moderate discrimination against hexaenoic species relative to monoenoic and dienoic species was observed at 0.25 mM. The addition of palmitoyl-CoA (7.5 μM) significantly enhanced cholinephosphotransferase activity when tetraenoic diacylglycerols were added at 0.25 or 0.40 mM. CDPethanolamine at 24.4 μM was found to inhibit the rates of phosphatidylcholine biosynthesis by 54 and 39% with hexaenoic and monoenoic 1,2-diacyl-sn-glycerols, respectively, whereas no significant effects were observed in the case of dienoic and tetraenoic species. These latter findings may partially explain why 1-saturated 2-docosahexaenoyl diacylglycerols are used to a greater extent for phosphatidylethanolamine than for phosphatidylcholine synthesis in rat liver in vivo. The present results also suggest that the selectivity of the cholinephosphotransferase for certain molecular species of 1,2-diacyl-sn-glycerols is a function of diacylglycerol concentration and may be mediated under physiological conditions by substrates for enzymes which compete for common diacylglycerol precursors.

scholarly journals Inhibition and Induction by Poziotinib of Different Rat Cytochrome P450 Enzymes In Vivo and in an In Vitro Cocktail Method

2021 ◽  
Vol 11 ◽  
Author(s):  
Jinhui Wang ◽  
Feifei Chen ◽  
Hui Jiang ◽  
Jia Xu ◽  
Deru Meng ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Rat Liver ◽  
Clinical Investigation ◽  
Liver Microsomes ◽  
Pharmacokinetic Parameters ◽  
Rat Liver Microsomes ◽  
Cytochrome P450 Enzymes ◽  
Significant Difference

Poziotinib is an orally active, irreversible, pan-HER tyrosine kinase inhibitor used to treat non-small cell lung cancer, breast cancer, and gastric cancer. Poziotinib is currently under clinical investigation, and understanding its drug-drug interactions is extremely important for its future development and clinical application. The cocktail method is most suitable for evaluating the activity of cytochrome P450 enzymes (CYPs). As poziotinib is partially metabolized by CYPs, cocktail probes are used to study the interaction between drugs metabolized by each CYP subtype. Midazolam, bupropion, dextromethorphan, tolbutamide, chlorzoxazone, phenacetin, and their metabolites were used to examine the effects of poziotinib on the activity of cyp1a2, 2b1, 2d1, 2c11, 2e1, and 3a1/2, respectively. The in vitro experiment was carried out by using rat liver microsomes (RLMs), whereas the in vivo experiment involved the comparison of the pharmacokinetic parameters of the probes after co-administration with poziotinib to rats to those of control rats treated with only probes. UPLC-MS/MS was used to detect the probes and their metabolites in rat plasma and rat liver microsomes. The in vitro results revealed that the half-maximal inhibitory concentration values of bupropion and tolbutamide in RLMs were 8.79 and 20.17 μM, respectively, indicating that poziotinib showed varying degrees of inhibition toward cyp2b1 and cyp2c11. Poziotinib was a competitive inhibitor of cyp2b1 and cyp2c11, with Ki values of 16.18 and 17.66 μM, respectively. No time- or concentration-dependence of inhibition by poziotinib was observed toward cyp2b1 and cyp2c11 in RLMs. Additionally, no obvious inhibitory effects were observed on the activity of cyp1a2, cyp2d1, cyp2e1, and cyp3a1/2. In vivo analysis revealed that bupropion, tolbutamide, phenacetin, and chlorzoxazone showed significantly different pharmacokinetic parameters after administration (p < 0.05); there was no significant difference in the pharmacokinetic parameters of dextromethorphan and midazolam. These results show that poziotinib inhibited cyp2b1 and cyp2c11, but induced cyp1a2 and cyp2e1 in rats. Thus, poziotinib inhibited cyp2b1 and cyp2c11 activity in rats, suggesting the possibility of interactions between poziotinib and these CYP substrates and the need for caution when combining them in clinical settings.

Inhibitory effects of the medicinal herb, Thonningia san gunea, on liver drug metabolizing enzymes of rats

2000 ◽  
Vol 19 (11) ◽  
pp. 623-631 ◽  
Author(s):  
M A Gyamfi ◽  
N Hokama ◽  
K Oppong-Boachie ◽  
Y Aniya
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Glutathione S Transferase ◽  
P450 Monooxygenase ◽  
Significant Difference ◽  
Cytosolic Glutathione ◽  
Thonningia Sanguinea

In this study we examined the effect of the aqueous extract of Thonningia sanguinea (T.S.) on 7-ethoxyresorufin 0- deethylase (EROD, CYPlAl), 7-pentoxyresorufin-dealkylase (PROD, CYP2B1/2), 7-methoxyresorufin 0- demethylase (MROD, CYP1A2), aniline hydroxylase (aniline, CYP2E1), p-nitrophenol hydroxylase (PNPH, CYP2E1) and erythromycin N-demethylase (ERDM, CYP3A1) in rat liver in vitro and in vivo. Although T.S. extract increased ERDM activity in induced rat liver microsomes, it showed a dose-dependent inhibitory effectin vitro on other P450 monooxygenase activities particularly EROD and PROD, which are mediated primarily by CYPlAl and CYP2B1/2, respectively. PROD, EROD and MROD activities were also decreased by 18%, 19% and 40%, respectively, in hepatic microsomes prepared from rats treated with T.S. extract for 3 days. Kinetic analysis of CYP activity of 3-methylchloranthrene-induced microsomes demonstrated that T.S. inhibited EROD and MROD activities by a noncompetitive and competitive mechanism, respectively. The analysis of alterations produced by T.S. on PROD kinetic parameters in phenobarbital-induced microsomes suggested that the inhibition is noncompetitive. Pretreatment of rats with T.S. prolonged pentobarbital and phenobarbital sleeping time; however, plasma phenobarbital concentration determined on awakening showed no significant difference between control and T.S.-treated rats. T.S. was also found to be a potent inhibitor of the liver cytosolic glutathione S-transferase. These data suggest that selective modulation of CYP isoenzymes by T.S. might con-tribute to protection of the liver from xenobiotic-induced intoxication or to alteration of the action of drug (s) conco-mitantly administered besides its antioxidative properties.

In Vitro Metabolism of E2, G2: Novel Bile Acid-Coupling Camptothecin Analogues, in Rat Liver Microsomes

2021 ◽  
Vol 16 ◽  
Author(s):  
Xiangli Zhang ◽  
Qin Shen ◽  
Yi Wang ◽  
Leilei Zhou ◽  
Qi Weng ◽  
...  
Keyword(s):  
Bile Acid ◽  
Phase I ◽  
Rat Liver ◽  
Deoxycholic Acid ◽  
Liver Microsomes ◽  
Intrinsic Clearance ◽  
Rat Liver Microsomes ◽  
Camptothecin Analogues

Background: E2 (Camptothecin - 20 (S) - O- glycine - deoxycholic acid), and G2 (Camptothecin - 20 (S) - O - acetate - deoxycholic acid) are two novel bile acid-derived camptothecin analogues by introducing deoxycholic acid in 20-position of CPT(camptothecin) with greater anticancer activity and lower systematic toxicity in vivo. Objective: We aimed to investigate the metabolism of E2 and G2 by Rat Liver Microsomes (RLM). Methods: Phase Ⅰ and Phase Ⅱ metabolism of E2 and G2 in rat liver microsomes were performed respectively, and the mixed incubation of phase I and phase Ⅱ metabolism of E2 and G2 was also processed. Metabolites were identified by liquid chromatographic/mass spectrometry. Results: The results showed that phase I metabolism was the major biotransformation route for both E2 and G2. The isoenzyme involved in their metabolism had some difference. The intrinsic clearance of G2 was 174.7mL/min. mg protein, more than three times of that of E2 (51.3 mL/min . mg protein), indicating a greater metabolism stability of E2. 10 metabolites of E2 and 14 metabolites of G2 were detected, including phase I metabolites (mainly via hydroxylations and hydrolysis) and their further glucuronidation products. Conclusion: These findings suggested that E2 and G2 have similar biotransformation pathways except some difference in the hydrolysis ability of the ester bond and amino bond from the parent compounds, which may result in the diversity of their metabolism stability and responsible CYPs(Cytochrome P450 proteins).

scholarly journals Interactions Between Ephedra sinica and Prunus armeniaca: From Stereoselectivity to Deamination as a Metabolic Detoxification Mechanism of Amygdalin

2021 ◽  
Vol 12 ◽  
Author(s):  
Yan Qin ◽  
Shanshan Wang ◽  
Qiuyu Wen ◽  
Quan Xia ◽  
Sheng Wang ◽  
...  
Keyword(s):  
Rat Liver ◽  
Metabolic Pathways ◽  
Liver Microsomes ◽  
Prunus Armeniaca ◽  
Rat Liver Microsomes ◽  
Microbial Enzymes ◽  
Ephedra Sinica ◽  
Metabolic Detoxification ◽  
Detoxification Pathway

Mahuang–Xingren (MX, Ephedra sinica Stapf-Prunus armeniaca L.) is a classic herb pair used in traditional Chinese medicine. This combined preparation reduces the toxicity of Xingren through the stereoselective metabolism of its main active ingredient amygdalin. However, whether stereoselectivity is important in the pharmacokinetic properties of amygdalin either in the traditional decoction or in the dispensing granules is unclear. Amygdalin is hydrolyzed to its metabolite, prunasin, which produces hydrogen cyanide by degradation of the cyano group. A comprehensive study of the metabolic pathway of amygdalin is essential to better understand the detoxification process. In this article, the potential detoxification pathway of MX is further discussed with regard to herb interactions. In this study, the pharmacokinetic parameters and metabolism of amygdalin and prunasin were investigated by comparing the traditional decoction and the dispensing granule preparations. In addition, several potential metabolites were characterized in an incubation system with rat liver microsomes or gut microbial enzymes. The combination of Xingren with Mahuang reduces exposure to D-amygdalin in vivo and contributes to its detoxification, a process that can be further facilitated in the traditional decoction. From the in vitro co-incubation model, 15 metabolites were identified and classified into cyanogenesis and non-cyanogenesis metabolic pathways, and of these, 10 metabolites were described for the first time. The level of detoxified metabolites in the MX traditional decoction was higher than that in the dispensing granules. The metabolism of amygdalin by the gut microbial enzymes occurred more rapidly than that by the rat liver microsomes. These results indicated that combined boiling both herbs during the preparation of the traditional decoction may induce several chemical changes that will influence drug metabolism in vivo. The gut microbiota may play a critical role in amygdalin metabolism. In conclusion, detoxification of MX may result 1) during the preparation of the decoction, in the boiling phase, and 2) from the metabolic pathways activated in vivo. Stereoselective pharmacokinetics and deamination metabolism have been proposed as the detoxification pathway underlying the compatibility of MX. Metabolic detoxification of amygdalin was quite different between the two combinations, which indicates that the MX decoctions should not be completely replaced by their dispensing granules.

Inhibitory Effect of Resveratrol on the Pharmacokinetics of Ticagrelor in Vivo and Vitro

2021 ◽  
Author(s):  
Peng Wang ◽  
Xiao-Xia Hu ◽  
Ying-hui Li ◽  
Nan-Yong Gao ◽  
Guo-quan Chen ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
In Vitro Study ◽  
Inhibitory Effect ◽  
Control Group ◽  
Rat Liver Microsomes ◽  
Sprague Dawley ◽  
Group B

This study was to evaluate the effect of resveratrol on the pharmacokinetics of ticagrelor in rats and the metabolism of ticagrelor in human CYP3A4 and liver microsomes. Eighteen Sprague-Dawley rats were randomly divided into three groups: group A (control group), group B (50mg/kg resveratrol), and group C (150mg/kg resveratrol ). After 30 minutes administration of resveratrol, a single dose of ticagrelor (18mg/kg) was administered orally. The vitro experiment was performed to examine the influence of resveratrol on ticagrelor metabolism in CYP3A4*1, human, and rat liver microsomes. Serial biological samples were assayed by validated UHPLC-MS/MS methods. In vivo study, the AUC and Cmax of ticagrelor in group B and C appeared to be significantly higher than the control group, while Vz/F and CLz/F of ticagrelor in group B and C were significantly decreased. In vitro study, resveratrol exhibited an inhibitory effect on CYP3A4*1, human and rat liver microsomes. The IC50 values of resveratrol were 56.75μM，69.07μM and 14.22μM, respectively. Our results indicated that resveratrol had a inhibitory effect on the metabolism of ticagrelor in vitro and vivo. It should be paid more attention to the clinical combination of resveratrol with ticagrelor and ticagrelor plasma concentration should be monitored to avoid the occurrence of adverse reaction.

The relative utilization of different molecular species of unsaturated 1,2-diacylglycerols by the acyl-CoA: 1,2-diacyl-sn-glycerol acyltransferase in rat liver microsomes

1977 ◽  
Vol 55 (11) ◽  
pp. 1186-1190 ◽  
Author(s):  
B.J. Holub ◽  
J. Piekarski
Keyword(s):  
Docosahexaenoic Acid ◽  
Rat Liver ◽  
Molecular Species ◽  
Liver Microsomes ◽  
Diacylglycerol Acyltransferase ◽  
Rat Liver Microsomes ◽  
Low Level ◽  
Triacylglycerol Synthesis ◽  
Relative Utilization ◽  
Assay Conditions

The possible selectivity of the acyl-CoA:1,2-diacyl-sn-glycerol acyltransferase in rat liver microsomes towards different molecular species of 1,2-diacyl-sn-glycerols was studied. Triacylglycerol synthesis was determined by monitoring the entry of radioactive palmitate from [1-14C]palmitoyl-CoA into triacylglycerol in the presence of various diacylglycerols. The diacylglycerol acyltransferase did not exhibit any selectivity against hexaenoic precursors under the assay conditions used (0.25 mM diacylglycerol in medium) and the rates of triacylglycerol synthesis observed with the various diacylglycerols were not significantly different when the data were analyzed statistically. The results suggest that the extremely low level of docosahexaenoic acid in triacylglycerols cannot be attributed to a discrimination of the diacylglycerol acyltransferase against 1-saturated 2-docosahexaenoyl precursors.

scholarly journals Inhibition of phosphatidylcholine synthesis by vasopressin and angiotensin in rat hepatocytes

1982 ◽  
Vol 208 (2) ◽  
pp. 453-457 ◽  
Author(s):  
S Alemany ◽  
I Varela ◽  
J M Mato
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Hepatocytes ◽  
Rat Liver Microsomes ◽  
Isolated Rat Hepatocytes ◽  
Fast Transient ◽  
Phosphatidylcholine Synthesis ◽  
Isolated Rat

The addition of 1 microM-vasopressin or -angiotensin to isolated rat hepatocytes induced a fast transient inhibition of the rate of incorporation of [Me-3H]choline into phosphatidylcholine. The cationophore A23187 induced a similar inhibition of phosphatidylcholine synthesis. The addition of micromolar Ca2+ to rat liver microsomes inhibited the activity of CDP-choline: 1,2-diacylglycerol cholinephosphotransferase. This inhibition is due a decrease in the Vmax. of the enzyme without affecting the Km for CDP-choline. It is concluded that Ca2+ regulates phosphatidylcholine synthesis in rat liver.

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