Document Detail

Hepatic oxidative drug metabolism and the microsomal milieu in a rat model of congenital hyperbilirubinemia.
MedLine Citation:
PMID:  3778508     Owner:  NLM     Status:  MEDLINE    
The aims of this study were to evaluate the hypothesis that impaired glucuronidation of bilirubin and possibly of drug oxidation in the liver of homozygous (jj) Gunn rats may be due to an altered microsomal milieu. Accordingly, we investigated and compared in vivo and in vitro demethylation of aminopyrine, hepatic cytochrome P-450 levels, microsomal lipid composition, and microsomal membrane fluidity in icteric, homozygous (jj) Gunn rats and in their anicteric heterozygous (jJ) littermates. In both males and females, [14C]aminopyrine demethylation in vivo, using the 14CO2 breath test, was unimpaired in the icteric animals. Likewise, cytochrome P-450 levels in the icteric and nonicteric groups were similar, and aminopyrine kinetics in vitro in the females were comparable in icteric and nonicteric littermates. The main lipid classes were also similar in the homozygous and heterozygous female Gunn rats, whereas only minor changes were seen in the phospholipid fatty acyl composition with a small, but significant, increase in the unsaturated index in the icteric group. Despite this, there was no apparent effect on hepatic microsomal membrane fluidity as measured by the order parameter of I[12,3] and the rotational correlation time of I[1,14] in either female or male sets of homozygous and heterozygous Gunn rats. Our data, therefore, do not support an alteration of composition or fluidity of the microsomal milieu as a mechanism of impaired bilirubin glucuronidation and possibly of oxidation in these animals. They also absolve long-term unconjugated hyperbilirubinemia as a mechanism of hepatic microsomal dysfunction. Our study, therefore, indirectly suggests that abnormal glucuronidation of bilirubin and some other aglycones in homozygous Gunn rats is due to genetic abnormalities involving the enzyme(s) itself.
C G Meredith; B B Muhoberac; J P Gray; K V Speeg; D Dunn; A M Hoyumpa; S Schenker
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemical pharmacology     Volume:  35     ISSN:  0006-2952     ISO Abbreviation:  Biochem. Pharmacol.     Publication Date:  1986 Nov 
Date Detail:
Created Date:  1986-11-28     Completed Date:  1986-11-28     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0101032     Medline TA:  Biochem Pharmacol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  3831-7     Citation Subset:  IM    
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MeSH Terms
Aminopyrine / metabolism
Aminopyrine N-Demethylase / metabolism
Bilirubin / metabolism*
Breath Tests
Cell Membrane / metabolism
Cytochrome P-450 Enzyme System / metabolism
Hyperbilirubinemia, Hereditary / metabolism*
Microsomes, Liver / abnormalities,  metabolism*
Rats, Gunn
Grant Support
Reg. No./Substance:
58-15-1/Aminopyrine; 635-65-4/Bilirubin; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.5.3.-/Aminopyrine N-Demethylase

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