Details

Autor(en) / Beteiligte

• Lubet, Ronald A.
• Mayer, Richard T.
• Cameron, John W.
• Nims, Raymond W.
• Burke, M.Danny
• Wolff, Thomas
• Guengerich, F.Peter

Titel

Dealkylation of pentoxyresorufin: A rapid and sensitive assay for measuring induction of cytochrome(s) P-450 by phenobarbital and other xenobiotics in the rat

Ist Teil von

• Archives of biochemistry and biophysics, 1985-04, Vol.238 (1), p.43-48

Ort / Verlag

San Diego, CA: Elsevier Inc

Erscheinungsjahr

1985

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• The O-dealkylation of pentoxyresorufin (7-pentoxyphenoxazone) by rat liver microsomes was examined. The reaction appeared highly specific for certain phenobarbital inducible forms of cytochrome P-450 and was increased 95- to 140-fold by animal pretreatment with phenobarbital (75 mg/kg/day, four ip injections) and ~50-fold by Aroclor 1254 (500 mg/kg, one ip injection) while animal pretreatment with 3-methylcholanthrene (50 mg/kg/day, three ip injections) resulted in less than a 2-fold increase over the rate detected in control microsomes. It was observed that this activity, in microsomes for Aroclor-pretreated rats, was dependent on O 2 and was inhibited by metyrapone and SKF 525-A, indicative of cytochrome(s) P-450 mediation in the reaction. When antibodies directed against purified cytochrome(s) P-450S were employed to inhibit the pentoxyresorufin O-dealkylation reaction, antibodies to P-450 PB-B greatly inhibited the reaction (>90%), while antibodies to P-450 PB-C or P-450 PB/PCN-E had minimal effects. Assay of hepatic microsomes from rats which were pretreated with varying doses of phenobarbital (0.9–75 mg/kg/day, four ip injections) indicated that while aminopyrine- N-demethylase activity was induced only 2-fold at the maximum dose (75 mg/kg/day), pentoxyresorufin O-dealkylase activity was induced ~140-fold at this dose and ~4-fold by a dose of phenobarbital as low as 0.9 mg/kg.