Document Detail


Cytochrome P-450 b and c in the rat brain and pituitary gland.
MedLine Citation:
PMID:  3275864     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A quantitative assessment of the levels of cytochromes P-450 b and P-450 c in the brains and pituitary glands of untreated and beta-naphthoflavone (BNF)-pretreated rats was made with polyclonal antibodies raised against hepatic P-450 b and c and the sensitive fluorometric assay of P-450 catalytic activity, namely, the O-deethylation of ethoxycoumarin (ETC). In the microsomal fraction of brains of untreated rats, the rate of formation of 7-hydroxycoumarin from ETC ranged between 0.1 and 20 pmol/min/mg of microsomal protein, which is approximately 0.01-2% of the level of hepatic microsomes of phenobarbital-induced rats. This brain activity was completely inhibited by anti P-450 b antibodies but was unaffected by anti P-450 c antibodies. As with hepatic P-450 b, metyrapone and chloramphenicol (100 microM) were good inhibitors of catalytic activity, whereas alpha-naphthoflavone (1 microM) was a poor inhibitor. No ETC O-deethylase activity was detectable in microsomes prepared from the pituitary glands of untreated rats. Upon pretreatment of rats with BNF, there was induction of ETC O-deethylase activity in the pituitary gland to a level of 3.3 +/- 1.5 pmol/min/mg of microsomal protein, but there was no significant increase in the level of activity in brain microsomes. Despite this, there was evidence of induction of P-450 c in both the brain and pituitary of BNF-pretreated rats since anti P-450 c antibodies inhibited brain activity by 55% and pituitary activity by 84%. The regional distribution of P-450 b and c in the hypothalamic-preoptic area and olfactory bulbs was examined. The level of ETC O-deethylase activity in the hypothalamic-preoptic area was not different from that in the whole brain, but in the olfactory bulbs activity was higher than that in whole brain, with a range of 0.1-52 pmol/min/mg of microsomal protein. The catalytic activity in the whole brain and in the olfactory bulbs was inhibited by anti P-450b but not by anti P-450c antibodies. Neither estradiol, testosterone, dehydrotestosterone, nor 5 alpha-androstane,3 beta,17 beta-diol (100 microM) competitively inhibited ETC O-deethylase activity, indicating that P-450 b is not responsible for the steroid hydroxylations previously reported in the brain. BNS pretreatment of rats did not cause a consistent increase in ETC O-deethylase upon BNF induction. However, there was an induction of P-450 c in the olfactory bulbs since catalytic activity was inhibited with anti P-450c antibodies.(ABSTRACT TRUNCATED AT 400 WORDS)
Authors:
B M Näslund; H Glaumann; M Warner; J A Gustafsson; T Hansson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Molecular pharmacology     Volume:  33     ISSN:  0026-895X     ISO Abbreviation:  Mol. Pharmacol.     Publication Date:  1988 Jan 
Date Detail:
Created Date:  1988-02-20     Completed Date:  1988-02-20     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0035623     Medline TA:  Mol Pharmacol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  31-7     Citation Subset:  IM    
Affiliation:
Department of Medical Nutrition, Huddinge University Hospital, Sweden.
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MeSH Terms
Descriptor/Qualifier:
7-Alkoxycoumarin O-Dealkylase
Animals
Benzoflavones / pharmacology
Brain / enzymology*,  ultrastructure
Cell Compartmentation
Cytochrome P-450 Enzyme System / metabolism*
Immunologic Techniques
Microscopy, Electron
Oxygenases / antagonists & inhibitors,  metabolism*
Pituitary Gland / enzymology*,  ultrastructure
Rats
Subcellular Fractions / enzymology
beta-Naphthoflavone
Chemical
Reg. No./Substance:
0/Benzoflavones; 6051-87-2/beta-Naphthoflavone; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.13.-/Oxygenases; EC 1.14.13.-/7-Alkoxycoumarin O-Dealkylase

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