scholarly journals Segregation of the polypeptide translocation apparatus to regions of the endoplasmic reticulum containing ribophorins and ribosomes. I. Functional tests on rat liver microsomal subfractions.

1984 ◽  
Vol 99 (6) ◽  
pp. 2247-2253 ◽  
Author(s):  
A Amar-Costesec ◽  
J A Todd ◽  
G Kreibich
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Placental Lactogen ◽  
Translation System ◽  
Secretory Proteins ◽  
Rat Liver Microsomes ◽  
Functional Tests ◽  
Membrane Bound

A preparation of rat liver microsomes containing 70% of the total cellular endoplasmic reticulum (ER) membranes was subfractionated by isopycnic density centrifugation. Twelve subfractions of different ribosome content ranging in density from 1.06 to 1.29 were obtained and analyzed with respect to marker enzymes, RNA, and protein content, as well as the capacity of these membranes to bind 80S ribosomes in vitro. After removal of native polysomes from these microsomal subfractions by puromycin in a buffer of high ionic strength their capacity to rebind 80S ribosomes approached levels found in the corresponding native membranes before ribosome stripping. This indicates that in vitro rebinding of ribosomes occurs to the same sites occupied in the cell by membrane-bound polysomes. Microsomes in the microsomal subfractions were also tested for their capacity to effect the translocation of nascent secretory proteins into the microsomal lumen utilizing a rabbit reticulocyte translation system programmed with mRNA coding for the precursor of human placental lactogen. Membranes from microsomes with the higher isopycnic density and a high ribosome content showed the highest translocation activity, whereas membranes derived from smooth microsomes had only a very low translocation activity. These results indicate the membranes of the rough and smooth portions of the endoplasmic reticulum are functionally differentiated so that sites for ribosome binding and the translocation of nascent polypeptides are segregated to the rough domain of the organelle.

scholarly journals Segregation of the polypeptide translocation apparatus to regions of the endoplasmic reticulum containing ribophorins and ribosomes. II. Rat liver microsomal subfractions contain equimolar amounts of ribophorins and ribosomes.

1984 ◽  
Vol 99 (6) ◽  
pp. 2254-2259 ◽  
Author(s):  
E E Marcantonio ◽  
A Amar-Costesec ◽  
G Kreibich
Keyword(s):  
Endoplasmic Reticulum ◽  
Western Blot ◽  
Rat Liver ◽  
Gel Electrophoresis ◽  
Liver Microsomes ◽  
Molar Ratio ◽  
Rat Liver Microsomes ◽  
Radioimmune Assay ◽  
Membrane Bound ◽  
Translational Process

Ribophorins I and II, two transmembrane glycoproteins characteristic of the rough endoplasmic reticulum (ER) are thought to be part of the translocation apparatus for proteins made on membrane bound polysomes. To study the stoichiometry between ribophorins and membrane-bound ribosomes we have determined the RNA and ribophorin content in rat liver microsomes or in microsomal subfractions of different density (i.e., ribosome content). The specificity of antibodies against the ribophorins was demonstrated by Western blot analysis of rat liver rough microsomes separated by 2-dimensional gel electrophoresis. The ribophorin content of microsomal subfractions was determined by indirect immunoprecipitation and for ribophorin I by a radioimmune assay. In the latter assay a molar ratio of ribophorin I/ribosomes approaching one was calculated for total microsomes as well as in the gradient subfractions. We therefore suggest that ribophorins mediate the binding of ribosomes to endoplasmic reticulum membranes or play a role in co-translational process which depend on this binding, such as the insertion of nascent polypeptides into the membrane or their transfer into the cisternal lumen.

In vitro metabolism in Sprague–Dawley rat liver microsomes of forsythoside A in different compositions of Shuang–Huang–Lian

Fitoterapia ◽  
2011 ◽  
Vol 82 (8) ◽  
pp. 1222-1230 ◽  
Author(s):  
Wei Zhou ◽  
Liu-qing Di ◽  
Jin-jun Shan ◽  
Xiao-lin Bi ◽  
Le-tian Chen ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
In Vitro Metabolism ◽  
Rat Liver Microsomes ◽  
Sprague Dawley ◽  
Sprague Dawley Rat

scholarly journals In Vitro Characterization of Borneol Metabolites by GC--MS Upon Incubation with Rat Liver Microsomes

2008 ◽  
Vol 46 (5) ◽  
pp. 419-423 ◽  
Author(s):  
R. Zhang ◽  
C.-h. Liu ◽  
T.-l. Huang ◽  
N.-s. Wang ◽  
S.-q. Mi
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
In Vitro Characterization

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).

In vitro metabolism of T-2 toxin by rat liver microsomes

1986 ◽  
Vol 34 (5) ◽  
pp. 865-868 ◽  
Author(s):  
Catherine A. Knupp ◽  
Steven P. Swanson ◽  
William B. Buck
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
In Vitro Metabolism ◽  
Rat Liver Microsomes

THE ROLE OF THE ADRENAL GLAND IN THE CONTROL OF AMINO ACID INCORPORATION INTO PROTEIN OF ISOLATED RAT LIVER MICROSOMES

1960 ◽  
Vol 21 (2) ◽  
pp. 177-189 ◽  
Author(s):  
A. KORNER
Keyword(s):  
Amino Acid ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Female Rats ◽  
Male Rats ◽  
Rat Liver Microsomes ◽  
Hypophysectomized Rats ◽  
Normal Rat ◽  
Secondary Result

SUMMARY 1. Microsomes, isolated from rat liver a day after adrenalectomy, incorporate more radioactive amino acid into their protein in vitro than microsomes from normal rat liver. This enhanced rate of incorporation progressively declines with time after adrenalectomy until it reaches a plateau level which is below the normal rate of incorporation. 2. Following adrenalectomy microsomes isolated from liver of male rats show a greater rise in incorporating ability than those from liver of female rats, and maintain it longer. 3. Most of the increased incorporation observed in the in vitro system soon after adrenalectomy of the rat, and most of the decreased incorporation observed in rats adrenalectomized for some time, results from alterations in the microsomes which change their ability to incorporate activated amino acids into proteins. 4. Treatment of rats with cortisol acetate results in an increase in the ability of liver microsomes to incorporate amino acid into protein. This heightened incorporating ability is probably a secondary result of the breakdown of extrahepatic tissue protein which is stimulated by cortisol. 5. Somewhat similar responses to acute adrenalectomy and to treatment with cortisol were found in hypophysectomized rats. 6. The protein anabolic response of adrenalectomized rats to treatment with insulin, and of adrenalectomized-hypophysectomized rats to treatment with insulin or growth hormone, is greater than that shown by rats which possess adrenal glands.

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