Related Experiment Video

Updated: Oct 17, 2026

Formation of Covalent DNA Adducts by Enzymatically Activated Carcinogens and Drugs In Vitro and Their Determination by 32P-postlabeling
09:33

Formation of Covalent DNA Adducts by Enzymatically Activated Carcinogens and Drugs In Vitro and Their Determination by 32P-postlabeling

Published on: March 20, 2018

Effect of 4-tert-octylphenol on cytochrome P450 enzymes in rat liver

N Hanioka1, H Jinno, Y S Chung

  • 1Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan. hanioka@nihs.go.jp

Archives of Toxicology
|March 31, 2000
PubMed

Insights

4-tert-octylphenol (OP) significantly alters male-specific cytochrome P450 enzymes in rat liver, impacting testosterone metabolism and potentially contributing to OP toxicity. These findings highlight OP

Area of Science:

  • Toxicology
  • Biochemistry
  • Pharmacology

Background:

  • Cytochrome P450 (CYP) enzymes are crucial for xenobiotic metabolism and endogenous compound regulation.
  • 4-tert-octylphenol (OP) is an environmental endocrine disruptor with known toxic effects.
  • Understanding OP's impact on hepatic CYP enzymes is vital for assessing its toxicological profile.

Purpose of the Study:

  • To investigate the effects of 4-tert-octylphenol (OP) on specific hepatic cytochrome P450 (CYP) enzyme activities and protein levels in rats.
  • To determine which CYP isoforms are most sensitive to OP exposure.
  • To correlate changes in CYP activity with OP toxicity.

Main Methods:

  • Rats were administered intraperitoneal injections of OP at varying doses (5, 10, 20 mg/kg).
  • Measurement of various CYP-dependent monooxygenase activities, including testosterone 2alpha-hydroxylase and testosterone 6beta-hydroxylase.
  • Immunoblotting was used to assess CYP2C11 and CYP3A2 protein levels.
  • Determination of intrinsic clearance (Cl(int)) values for specific enzyme activities.

Main Results:

  • OP significantly decreased testosterone 2alpha-hydroxylase (CYP2C11-associated) activity at all doses.
  • Testosterone 6beta-hydroxylase (CYP3A2-associated) activity was reduced by OP at the highest dose.
  • OP treatment led to decreased protein levels of CYP2C11 and CYP3A2, with activity reductions exceeding protein level changes.
  • Intrinsic clearance values for testosterone 2alpha-hydroxylase and, at higher doses, testosterone 6beta-hydroxylase were significantly reduced.
  • 7-ethoxycoumarin O-deethylase activity was also decreased, while other CYP activities remained unaffected.

Conclusions:

  • 4-tert-octylphenol (OP) selectively affects male-specific CYP isoforms (CYP2C11, CYP3A2) in rat liver.
  • The observed alterations in CYP enzyme activity and protein levels are closely linked to the toxic effects of OP.
  • These findings contribute to understanding the mechanism of OP-induced toxicity through modulation of hepatic drug-metabolizing enzymes.

More Related Videos

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces08:50

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

Published on: September 26, 2014

In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver10:38

In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver

Published on: May 4, 2016

Related Concept Videos

Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes01:28

Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes

Cytochrome P450 (CYP450) enzymes are a superfamily of heme-containing monooxygenases that play a pivotal role in Phase I drug metabolism by catalyzing oxidation and reduction reactions.These enzymes transform lipophilic xenobiotics into more hydrophilic metabolites, facilitating subsequent Phase II conjugation and eventual excretion. The CYP450 family is classified into families (e.g., CYP1–CYP3) and subfamilies (e.g., CYP2A, CYP2C), based on amino acid sequence homology.CYP450 isoenzymes,...
Phase I Reactions: Oxidation of Aliphatic and Aromatic Carbon-Containing Systems01:19

Phase I Reactions: Oxidation of Aliphatic and Aromatic Carbon-Containing Systems

Phase I biotransformation reactions are integral to drug metabolism, predominantly involving oxidative, reductive, and hydrolytic transformations. Chief among these are oxidative reactions, which enhance the hydrophilicity of xenobiotics and introduce polar functional groups to facilitate their elimination from the body.
Oxidation reactions are fundamental in aromatic carbon-containing systems. An example is the hydroxylation of phenobarbital, a process that transforms it into...
Effect of Hepatic Disease on Pharmacokinetics: Drug Dosing and Hepatic Blood Flow01:26

Effect of Hepatic Disease on Pharmacokinetics: Drug Dosing and Hepatic Blood Flow

Chronic liver disease significantly impacts drug metabolism due to alterations in hepatic blood flow and enzyme accessibility. This disruption affects the body's pharmacokinetics—the movement and processing of drugs within the system. Key enzymes crucial for metabolizing medications become less accessible, changing how drugs are processed and utilized. Furthermore, liver disease influences the synthesis of plasma proteins, such as albumin and globulins, which play critical roles in drug binding...
Drug Metabolism: Phase I Reactions01:17

Drug Metabolism: Phase I Reactions

A phase I reaction is a biochemical process that introduces a functionally reactive polar group to a substance. This transformation predominantly occurs in the liver, facilitated by the cytochrome P450 system of hemoproteins situated in the lipophilic endoplasmic reticulum of cells. The metabolite generated through this process can have varying polarities. If it is sufficiently polar, it can be easily excreted in the urine due to its water compatibility. However, if the metabolite is nonpolar,...
Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test01:22

Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test

In clinical practice, the direct measurement of hepatic blood flow to evaluate liver function presents significant challenges due to the intricate and specialized nature of the necessary techniques. Consequently, healthcare professionals often rely on empirical estimates derived from thorough patient examinations and liver function tests to gauge liver health. Among the tools at their disposal, the Child–Pugh and MELD scoring systems stand out for their ability to categorize and assess the...
Bioactivation and Tissue Toxicity01:25

Bioactivation and Tissue Toxicity

Bioactivation is a metabolic process that transforms less reactive substances into highly reactive metabolites, initiating tissue toxicity. This transformation can lead to various toxic effects, including carcinogenesis and teratogenesis. Reactive metabolites are classified into two main types: electrophiles and free radicals.Electrophiles are electron-deficient species and are produced primarily by the enzyme cytochrome P-450 during the metabolism of compounds containing carbon, nitrogen, or...