scholarly journals Induction and repression of the major phenobarbital-induced cytochrome P-450 measured by radioimmunoassay

1983 ◽  
Vol 212 (1) ◽  
pp. 55-64 ◽  
Author(s):  
I R Phillips ◽  
E A Shephard ◽  
R M Bayney ◽  
S F Pike ◽  
B R Rabin ◽  
...  
Keyword(s):  
Rat Liver ◽  
Total Content ◽  
Fold Increase ◽  
Differential Effects ◽  
Microsomal Membranes ◽  
Fold Induction ◽  
Purified Antigen ◽  
Cytochrome P 450

Two independent radioimmunoassay techniques for the major phenobarbital-inducible cytochrome P-450 (PB P-450) of rat liver microsomal membranes are described. The first technique employs as the source of radiolabelled antigen the products of translation in vitro labelled with [35S]methionine. The second technique employs purified antigen labelled with 125I and is quicker, less expensive and more precise. Both assays are highly specific for PB P-450 and can detect quantities of this variant as small as 1 ng. This is several orders of magnitude more sensitive than any method described previously for the quantification of cytochromes P-450, and consequently the technique is particularly well suited for the quantification of so-called constitutive cytochrome P-450 variants that are present in very low amounts. The results of the radioimmunoassays demonstrate that the apparent 2.6-fold induction of total cytochromes P-450 after phenobarbital treatment is due to a 43-fold increase in Pb P-450. Although β-naphthoflavone increases the total content of cytochrome P-450 of microsomal membranes 1.4-fold, it actually causes a 55% decrease in the amount of PB P-450. Thus different xenobiotics can have differential effects on the expression of the genes for specific cytochrome P-450 variants.

Metabolism of n-hexane by rat liver and extrahepatic tissues and the effect of cytochrome P-450 inducers

1997 ◽  
Vol 16 (3) ◽  
pp. 131-137 ◽  
Author(s):  
Sarah J Crosbie ◽  
PG Blain ◽  
Faith M Williams
Keyword(s):  
Skeletal Muscle ◽  
Rat Liver ◽  
Fold Increase ◽  
Rat Tissues ◽  
Human Cytochrome ◽  
Extrahepatic Tissues ◽  
Mass Spectometry ◽  
Fast Twitch ◽  
Cytochrome P 450

1 The in vitro metabolism ofn-hexane was studied in rat liver, lung, brain and skeletal muscle microsomes and in microsomes prepared from cell lines expressing human cytochrome P-450 2E1 or 2B6. The hydro xylated metabolites ofn-hexane were quantified by gas chromatography-mass spectometry. 2 Rat liver and extensor digitorum longus (EDL, fast- twitch skeletal muscle) microsomes and the CYP 2B6 microsomes produced the pre-neurotoxic metabolite of n-hexane, 2-hexanol as a major metabolite in contrast to the other rat tissues examined. 3 Inhibition of 2- and 3-hexanol production from n- hexane by rat lung microsomes using metyrapone, an inhibitor of cytochrome P-450 2B1 activity, resulted in almost complete inhibition of lung microsomal activ ity. 4 Production of all three hexanols was significantly increased with phenobarbital-induced rat liver micro somes, with a 10-fold increase in 2- and 3-hexanol production. A slight increase in 2-hexanol production with phenobarbital-induced rat EDL and brain micro somes was observed. No increase in n-hexane meta bolism was noted following induction with β- naphthoflavone or with ethanol.

scholarly journals Quantification of NADPH: cytochrome P-450 reductase in liver microsomes by a specific radioimmunoassay technique

1983 ◽  
Vol 211 (2) ◽  
pp. 333-340 ◽  
Author(s):  
E A Shephard ◽  
I R Phillips ◽  
R M Bayney ◽  
S F Pike ◽  
B R Rabin
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Fold Increase ◽  
Molar Ratio ◽  
Nadph Cytochrome ◽  
Specific Radioimmunoassay ◽  
Microsomal Membranes ◽  
Cytochrome P 450

We have developed a specific radioimmunoassay to quantify NADPH: cytochrome P-450 reductase. The assay is based on the use of 125I-labelled NADPH: cytochrome P-450 reductase as the radiolabelled antigen and can detect quantities of this protein in amounts as low as 30 pg. The results of the radioimmunoassay demonstrates that the 2.7-fold increase in enzyme activity in rat liver microsomal membranes after phenobarbital treatment is due to increased amounts of the protein. beta-Naphthoflavone treatment, however, did not alter the activity or the quantity of this enzyme in microsomes. The quantification of NADPH: cytochrome P-450 reductase in the microsomes isolated from control and phenobarbital- and beta-naphthoflavone-treated animals permits the calculation of the ratio of this protein to that of total cytochromes P-450. A molar ratio of 15:1 (cytochromes P-450/NADPH: cytochrome P-450 reductase) was calculated for control and phenobarbital-treated animals. This ratio increased to 21:1 after beta-naphthoflavone treatment. Thus the molar ratio of these proteins in liver microsomes can vary with exposure of the animals to particular xenobiotics.

Isolation and expression of cDNA clones for a rat liver asialoglycoprotein receptor

1986 ◽  
Vol 6 (6) ◽  
pp. 527-534
Author(s):  
Colin Watts
Keyword(s):  
Rat Liver ◽  
Protein Sequence ◽  
Wheat Germ ◽  
Asialoglycoprotein Receptor ◽  
Cdna Clones ◽  
Oligonucleotide Probes ◽  
Synthetic Oligonucleotide ◽  
Microsomal Membranes ◽  
Synthetic Oligonucleotides

cDNA clones for the major rat liver asialoglycoprotein (ASGP) receptor were isolated from a phage λgtl 1 library using synthetic oligonucleotide probes corresponding to two regions of the protein sequence. The longest clone obtained encoded all but the first 11 codons of the receptor. The cDNA was completed with synthetic oligonucleotides and was used to direct the synthesis of mRNA for the receptor in vitro. Subsequent translation in a wheat germ lysate produced authentic ASGP receptor which assembled correctly into microsomal membranes.

scholarly journals Release of poly a(+) messenger RNA from rat liver rough microsomes upon disassembly of bound polysomes

1977 ◽  
Vol 74 (2) ◽  
pp. 414-427 ◽  
Author(s):  
J Kruppa ◽  
DD Sabatini
Keyword(s):  
Ionic Strength ◽  
Rat Liver ◽  
Messenger Rna ◽  
High Salt ◽  
Salt Medium ◽  
Ribosomal Subunits ◽  
Microsomal Membranes ◽  
Low Ionic Strength

Several procedures were used to disassemble rat liver rough microsomes (RM) into ribosomal subunits, mRNA, and ribosome-stripped membrane vesicles in order to examine the nature of the association between the mRNA of bound polysomes and the microsomal membranes. The fate of the mRNA molecules after ribosome release was determined by measuring the amount of pulse-labeled microsomal RNA in each fraction which was retained by oligo-dT cellulose or by measuring the poly A content by hybridization to radioactive poly U. It was found that ribosomal subunits and mRNA were simultaneously released from the microsomal membranes when the ribosomes were detached by: (a) treatment with puromycin in a high salt medium containing Mg++, (b) resuspension in a high salt medium lacking Mg++, and (c) chelation of Mg++ by EDTA or pyrophosphate. Poly A-containing mRNA fragments were extensively released from RM subjected to a mild treatment with pancreatic RNase in a medium of low ionic strength. This indicates that the 3' end of the mRNA is exposed on the outer microsomal surface and is not directly bound to the membranes. Poly A segments of bound mRNA were also accessible to [(3)H] poly U for in situ hybridization in glutaraldehyde-fixed RM. Rats were treated with drugs which inhibit translation after formation of the first peptide bonds or interfere with the initiation of protein synthesis. After these treatments inactive monomeric ribosomes, as well as ribosomes bearing mRNA, remained associated with their binding sites in microsomes prepared in media of low ionic strength. However, because there were no linkages provided by nascent chains, ribosomes, and mRNA, molecules were released from the microsomal membranes without the need of puromycin, by treatment with a high salt buffer containing Mg++. Thus, both in vivo and in vitro observations are consistent with a model in which mRNA does not contribute significantly to the maintenance of the interaction between bound polysomes and endoplasmic reticulum membranes in rat liver hepatocytes.

scholarly journals The association in vitro of polyribosomes with ribonuclease-treated derivatives of hepatic rough endoplasmic reticulum. Characteristics of the membrane binding sites and factors influencing association

1971 ◽  
Vol 125 (1) ◽  
pp. 67-79 ◽  
Author(s):  
T. K. Shires ◽  
L. Narurkar ◽  
H. C. Pitot
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Binding Capacity ◽  
Trypsin Treatment ◽  
Partial Removal ◽  
Adult Rat ◽  
Microsomal Membranes ◽  
Derivatives Of ◽  
Membrane Binding Sites

1. Pancreatic ribonuclease in dilute EDTA has been shown to condition rough-microsomal membranes from adult rat liver to accept exogenously added rat liver polyribosomes in vitro at 0–4°C. Treated smooth membranes would not significantly interact with polyribosomes. 2. The conditioning process decreased the membrane RNA content and removed polyribosomes from vesicle surfaces as viewed electron-microscopically. 3. Binding to these conditioned membranes was shown to be uninfluenced by changes of temperature (0–37°C) and pH (6.9–7.8) or the presence of cell sap, but was inhibited by increasing the concentration of potassium chloride. 4. Possession of a polyribosome-binding capacity by conditioned rough membranes was not dependent on adventitious materials that could be dislodged by high ionic strengths. 5. Trypsin treatment under mild conditions destroyed the binding capacity of ribonuclease-conditioned rough membranes. 6. A 2–10S residual RNA was recovered from ribonuclease-conditioned membranes, but its partial removal had no effect on the capacity of membranes to accept polyribosomes. However, some role for this residual RNA in attaching polyribosomes could not be discounted. 7. Evidence is considered that polyribosome-binding sites are intrinsic features of conditioned membranes isolated from rough-microsomal fractions, and that long-range ionic bonding is a primary factor in polyribosome interaction with these binding sites.

scholarly journals Biogenesis of endoplasmic reticulum proteins involved in Ca2+ signalling during megakaryocytic differentiation: an in vitro study

2000 ◽  
Vol 350 (3) ◽  
pp. 723-734 ◽  
Author(s):  
Christine LACABARATZ-PORRET ◽  
Sophie LAUNAY ◽  
Elisabeth CORVAZIER ◽  
Raymonde BREDOUX ◽  
Béla PAPP ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Western Blotting ◽  
Time Course ◽  
In Vitro Study ◽  
Fold Increase ◽  
Distinct Pattern ◽  
Platelet Glycoprotein ◽  
Protein Patterns ◽  
Fold Induction

The endoplasmic reticulum (ER) plays a key role in Ca2+ signalling through Ca2+ release via inositol 1,4,5-trisphosphate receptors (InsP3-Rs) and Ca2+ uptake by sarco/endoplasmic reticulum Ca2+-ATPases (SERCAs). Here, we investigated the organization of platelet ER and its biogenesis during megakaryocytopoiesis. First, erythro/megakaryoblastic MEG 01, UT7, M-O7e and CHRF 288-11 cell lines, platelets and thrombopoietin-induced UT7-Mpl cells were selected for the study of SERCA2b and SERCA3 proteins by Western blotting using the antibodies IID8 and PL/IM430, respectively. As judged by platelet glycoprotein IIIa (GPIIIa) expression, an increase in SERCA3 proteins was observed while that of SERCA2b remained unchanged throughout maturation. Second, these studies were extended to the newly described alternatively spliced SERCA3a–c RNAs and InsP3-Rs using the in vitro model of PMA-induced differentiation of MEG 01 cells. Time-course and dose–response studies showed a maximal approx. 4-fold up-regulation of SERCA3 proteins using 10-8 M PMA for 3 days, which paralleled induction of GPIIIa expression. SERCA3 induction was found to occur at the level of mRNA. The modulation of the different SERCA3 species (i.e. 3a, 3b and 3c) was isoform-specific: while SERCA3a was slightly increased, an approx. 3-fold induction of SERCA3b, and a 4-fold induction of SERCA3c, was observed after 24h of PMA treatment. Isoform-specific Western blotting and/or reverse transcriptase PCR studies showed that InsP3-R types I, II and III are expressed in MEG 01 cells, as well as in platelets. Study of the expression of these InsP3-R types in PMA-induced MEG 01 cells revealed that: (i) InsP3-RI protein and mRNA showed no changes; (ii) InsP3-RII mRNA was up-regulated and peaked at hour 48 and (iii) InsP3-RIII mRNA and protein showed a transitory maximal 3- and 2.3-fold increase at hours 6 and 30, respectively. Upon PMA treatment of CHRF 288-11 cells, in which GPIIIa is not induced upon treatment, a similar pattern of regulation of InsP3-R types II and III was seen, but a distinct pattern of SERCA3 regulation was observed. These results suggest a profound reorganization of ER-protein patterns during megakaryocytopoiesis and underline the role of SERCA3 gene regulation in the control of Ca2+-dependent platelet functions.

Carcinogenic Non-Aminoazo Dye 1-Phenylazo-2-hydroxynaphthalene (Sudan I) Is Oxidized by Rat Liver Microsomal Cytochrome P-450 to Metabolites Binding to Macromolecules (Nucleic Acids and Proteins)

1992 ◽  
Vol 57 (7) ◽  
pp. 1537-1546 ◽  
Author(s):  
Marie Stiborová ◽  
Pavel Anzenbacher
Keyword(s):  
Nucleic Acids ◽  
Rat Liver ◽  
Chemical Carcinogenesis ◽  
Reactive Metabolites ◽  
Reactive Metabolite ◽  
Microsomal Cytochrome ◽  
Sudan I ◽  
Cytochrome P 450

Carcinogenic non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I) is oxidized by microsomal cytochromes P-450 to reactive metabolite(s) binding to macromolecules (nucleic acids, proteins) in vitro. The extent of binding to macromolecules proceeded in the order: protein > rRNA > tRNA > DNA. The patern of products formed from Sudan I and binding of the reactive metabolites of this compound to macromolecules are dependent on the concentration of Sudan I, NADPH and on the duration of the incubation. The participation of the adducts formed with macromolecules in the initiation of chemical carcinogenesis is discussed.

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