Related Experiment Videos
Studies on pulmonary aryl hydrocarbon hydroxylase activity in inbred strains of mice
Abstract:
Pulmonary and hepatic levels of aryl hydrocarbon hydroxylase (AHH) were studied in inbred strains of mice following intratracheal (i.t.) instillation of 3-methylcholanthrene (MCA). I.t. instillation of 188 mug MCA in sterile 0.2% gelatin in saline resulted in preferential induction of pulmonary AHH. After treatment with this dose of MCA, the pulmonary AHH levels of strains C57BL/6Cum, C57BL/6J, BALB/cMai, C3H/fMai, and C57L/J were observed to be induced within 24 h after treatment. Strains DBA/2Cum, AKR/J, SJL/J, DBA/2J and RF/J expressed no such increase. At a dose of 500 mug MCA, the pulmonary tissue of DBA/2 mice did express a 4-fold increase. This increase in AHH was determined to be quite different from the increase observed in C57BL/6 mice by: (1) specific activity of the enzymes, (2) genetic regulation, (3) susceptibility to inhibition by 7,8-benzoflavone, and (4) spectral properties of the associated cytochromes. It was of major importance that induction of pulmonary AHH was observed to be regulated by a single dominant gene in crosses involving the C57BL/6Cum and DBA/2Cum strains of mice. Results were discussed with the view in mind that these genetically regulated levels of AHH may play a role in susceptibility to cancers induced by polycyclic aromatic hydrocarbon carcinogens.
Insights
Genetic differences in aryl hydrocarbon hydroxylase (AHH) induction in mouse lungs affect susceptibility to polycyclic aromatic hydrocarbon carcinogens. This study highlights the role of AHH genetic regulation in cancer risk.
Area of Science:
- Toxicology
- Pharmacogenetics
- Molecular Biology
Background:
- Aryl hydrocarbon hydroxylase (AHH) is a key enzyme in metabolizing polycyclic aromatic hydrocarbons (PAHs).
- Genetic variability in AHH induction can influence an organism's susceptibility to carcinogens.
- Understanding AHH regulation is crucial for assessing cancer risk from environmental pollutants.
Purpose of the Study:
- To investigate the strain-specific induction of pulmonary and hepatic AHH in mice after 3-methylcholanthrene (MCA) exposure.
- To characterize the differences in AHH induction between responsive and non-responsive mouse strains.
- To determine the genetic basis of AHH induction in mice.
Main Methods:
- Intratracheal instillation of 3-methylcholanthrene (MCA) in different mouse strains.
- Measurement of pulmonary and hepatic aryl hydrocarbon hydroxylase (AHH) activity.
- Analysis of enzyme specific activity, genetic regulation, inhibitor susceptibility, and spectral properties.
- Cross-breeding experiments to study the genetic control of AHH induction.
Main Results:
- Intratracheal MCA preferentially induced pulmonary AHH in C57BL/6Cum, C57BL/6J, BALB/cMai, C3H/fMai, and C57L/J mice within 24 hours.
- DBA/2Cum, AKR/J, SJL/J, DBA/2J, and RF/J strains showed no significant AHH induction at a lower MCA dose, but DBA/2 mice exhibited a 4-fold increase at a higher dose.
- Differences in AHH induction between C57BL/6 and DBA/2 mice were noted in enzyme activity, genetic regulation, 7,8-benzoflavone inhibition, and spectral properties.
- Pulmonary AHH induction was found to be regulated by a single dominant gene in crosses between C57BL/6Cum and DBA/2Cum strains.
Conclusions:
- Significant genetic variation exists in the induction of pulmonary aryl hydrocarbon hydroxylase (AHH) among inbred mouse strains.
- A single dominant gene primarily regulates pulmonary AHH induction in susceptible mouse crosses.
- Genetically regulated AHH levels may play a critical role in determining susceptibility to cancers induced by polycyclic aromatic hydrocarbon carcinogens.