scholarly journals EFFECTS OF LYOPHILIZATION AND STORAGE OF RAT LIVER MICROSOMES ON ACTIVITY OF ANILINE HYDROXYLASE, CONTENTS OF CYTOCHROME b5 AND CYTOCHROME P-450 AND ANILINE-INDUCED P-450 DIFFERENCE SPECTRUM

1974 ◽  
Vol 24 (2) ◽  
pp. 195-203 ◽  
Author(s):  
Tetsuya KAMATAKI ◽  
Haruo KITAGAWA
Keyword(s):  
Rat Liver ◽  
Cytochrome B5 ◽  
Liver Microsomes ◽  
Difference Spectrum ◽  
Rat Liver Microsomes ◽  
Aniline Hydroxylase ◽  
And Storage ◽  
Cytochrome P 450

scholarly journals Toxic dark effects of protoporphyrin on the cytochrome P-450 system in rat liver microsomes

1992 ◽  
Vol 288 (1) ◽  
pp. 155-159 ◽  
Author(s):  
M Williams ◽  
J Van der Zee ◽  
J Van Steveninck
Keyword(s):  
Kinetic Analysis ◽  
Rat Liver ◽  
Competitive Inhibition ◽  
Cytochrome B5 ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Erythropoietic Protoporphyria ◽  
Dependent Inhibition ◽  
Nadh Cytochrome ◽  
Cytochrome P 450

In erythropoietic protoporphyria, accumulation of protoporphyrin has been found in various tissues and liver cirrhosis occurs frequently in this disease, probably due to toxic dark effects of protoporphyrin. We have studied the effect of porphyrins on various enzymic functions in rat liver microsomes. Incubation of microsomes with protoporphyrin resulted in a concentration-dependent inhibition of the oxidation of 7-ethoxycoumarin and aminopyrine by the cytochrome P-450 system. Kinetic analysis showed a decrease in Vmax., whereas the Km was not affected (non-competitive inhibition). Furthermore, reduction of cytochrome c by the NADPH-cytochrome P-450 reductase and by the NADH-cytochrome b5 reductase was inhibited. However, the activity of the reductases was only affected when the microsomes were pre-incubated with protoporphyrin, and it was found that the inhibition was dependent on the duration of the pre-incubation. Kinetic analysis again revealed non-competitive inhibition. When these experiments were repeated with uroporphyrin, no inhibition could be observed. With Stern-Volmer plots it was demonstrated that this was most likely caused by the localization of the porphyrins: protoporphyrin is localized in the membrane, whereas uroporphyrin remains in solution. From these results it is concluded that accumulation of protoporphyrin in the liver may markedly affect the cytochrome P-450 system and thus its detoxification function.

scholarly journals Analytical study of microsomes and isolated subcellular membranes from rat liver. VI. Electron microscope examination of microsomes for cytochrome b5 by means of a ferritin-labeled antibody.

1976 ◽  
Vol 71 (2) ◽  
pp. 551-564 ◽  
Author(s):  
J Remacle ◽  
S Fowler ◽  
H Beaufay ◽  
A Amarcostesec ◽  
J Berthet
Keyword(s):  
Electron Microscope ◽  
Rat Liver ◽  
Sucrose Gradient ◽  
Analytical Study ◽  
Cytochrome B5 ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Microscope Examination ◽  
Group B ◽  
Isopycnic Centrifugation

The distribution of cytochrome b5 in rat liver microsomes, and in two microsomal subfractions isolated by density equilibration in a linear sucrose gradient, was studied under the electron microscope by means of a ferritin-labeled hybrid anti-cytochrome b5/anti-ferritin antibody. Results of this study show that cytochrome b5 is present in essentially all microsomal vesicles derived from endoplasmic reticulum (ER), whether rough or smooth. Thus, the dissociation of ER constituents into two groups (b and c), achieved by subfractionating microsomes by isopycnic centrifugation (Beaufay, H., A. Amar-Costesec, D. Thines-Sempoux, M. Wibo, M. Robbi, and J. Berthet. 1974. J. Cell Biol. 61:213-231), does not reflect the association of each group with distinct microsomal particles but reflects rather an enzymatic heterogeneity of the ER: the ratio of group c to group b enzymes increasing with the density and ribosome load of the particles.

Interlaboratory comparison of total cytochrome P-450 and protein determinations in rat liver microsomes

1987 ◽  
Vol 61 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Alphons A. J. J. L. Rutten ◽  
Hein E. Falke ◽  
Jan F. Catsburg ◽  
Randy Topp ◽  
Bas J. Blaauboer ◽  
...  
Keyword(s):  
Rat Liver ◽  
Interlaboratory Comparison ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Cytochrome P 450

Pituitary regulation of cytochrome P-450-mediated metabolism of steroids and xenobiotics in rat liver microsomes

1986 ◽  
Vol 7 (4) ◽  
pp. 575-582 ◽  
Author(s):  
Agneta Blanck ◽  
Anders Åström ◽  
Tiiu Hansson ◽  
Joseph W. De Pierre ◽  
Jan-Åke Gustafsson
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Cytochrome P 450
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