These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Reducing equivalents for mixed function oxidation in periportal and pericentral regions of the liver lobule in perfused livers from normal and phenobarbital-treated rats.
    Author: Belinsky SA, Kauffman FC, Thurman RG.
    Journal: Mol Pharmacol; 1984 Nov; 26(3):574-81. PubMed ID: 6333582.
    Abstract:
    The supply of NADPH for cytochrome P-450-dependent mixed function oxidation from the pentose cycle and mitochondria in periportal and pericentral regions of the liver lobule was evaluated in perfused rat liver. Rates of 7-ethoxycoumarin O-deethylation in livers from fed, normal rats monitored with micro-light guides placed on periportal and pericentral regions were 1.2 mumol/g/hr in both regions of the liver lobule. In livers from fed, phenobarbital-treated rats, rates were 3.6 and 7.0 mumol/g/hr in periportal and pericentral regions, respectively. Following treatment of rats with 6-aminonicotinamide, an inhibitor of the pentose cycle, rates of 7-hydroxycoumarin production were approximately 0.9 mumol/g/hr in both regions of the lobule in livers from normal rats and 2.1 and 3.4 mumol/g/hr in periportal and pericentral regions, respectively, in livers from phenobarbital-treated rats. Based on the difference in rates of 7-hydroxycoumarin production in the presence and absence of 6-aminonicotinamide, we conclude that the pentose cycle supplies NADPH for 7-ethoxycoumarin metabolism at rates around 0.3 mumol/g/hr in both regions of the liver lobule in livers from normal rats and 1.5 and 3.6 mumol/g/hr in periportal and pericentral regions, respectively, in livers from phenobarbital-treated rats. Potassium cyanide, an inhibitor of mitochondrial oxidation, reduced rates of 7-ethoxycoumarin O-deethylation to approximately 0.6 mumol/g/hr in both regions of the liver lobule in livers from fed, normal rats and to around 0.2 mumol/g/hr after fasting or treatment with 6-aminonicotinamide. In livers from fasted, phenobarbital-treated rats, 7-hydroxycoumarin was produced at rates of 0.3 and 0.7 mumol/g/hr in periportal and pericentral regions, respectively, in the presence of KCN. Decreases in rates of 7-hydroxycoumarin production during KCN infusion indicate that the mitochondria supply about 0.7 mumol of NADPH/g/hr for 7-ethoxycoumarin metabolism in both regions in livers from normal rats and 1.3 and 2.7 mumol/g/hr in periportal and pericentral regions in livers from phenobarbital-treated rats. The sum of KCN and 6-aminonicotinamide-sensitive rates of 7-ethoxycoumarin metabolism closely approximated rates measured in the absence of the inhibitors. These data indicate that mitochondria supply 50 to 70% of the reducing equivalents for mixed function oxidation of 7-ethoxycoumarin in both regions of the liver lobule in livers from fed rats.
    [Abstract] [Full Text] [Related] [New Search]