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Complementary DNA sequence of 3-methylcholanthrene-inducible P-450 from the rat lung
1Department of Cancer Chemotherapy and Prevention, Tohoku University, Sendai, Japan.
Abstract:
Cytochrome P-450MC was induced in pulmonary microsomes of 3-methylcholanthrene-treated rats and also at low level in that of isosafrole-treated rats. Cytochrome P-450d was not detected in the lungs of 3-methylcholanthrene- or isosafrole-treated rats by the method of Western blot analysis with a polyclonal antibody raised against cytochrome P-450c which is equally effective against P-450d, nor by the method of Northern hybridization probed with pcP450mc3 (P-450d probe). Complementary DNA of P-450MC was isolated from rat pulmonary cDNA library and the nucleotide sequence of pulmonary cDNA was compared with that of hepatic P-450c cDNA reported by Yabusaki et al. There was no gross change in nucleotide sequences of cDNA between pulmonary P-450MC and hepatic P-450c.
Insights
Cytochrome P-450MC is induced in rat lungs by 3-methylcholanthrene. Pulmonary P-450MC shows no significant nucleotide sequence difference compared to hepatic P-450c.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Cytochrome P-450 enzymes are crucial for xenobiotic metabolism.
- Investigating specific isoforms like P-450MC in different tissues is important for understanding drug and carcinogen metabolism.
- Previous studies have characterized hepatic forms, but pulmonary expression needs further elucidation.
Purpose of the Study:
- To investigate the induction and characteristics of Cytochrome P-450MC in rat pulmonary microsomes.
- To determine the presence or absence of Cytochrome P-450d in rat lungs following specific inducer treatments.
- To compare the nucleotide sequence of pulmonary P-450MC with its hepatic counterpart, P-450c.
Main Methods:
- Western blot analysis using a polyclonal antibody against cytochrome P-450c.
- Northern hybridization using a P-450d probe (pcP450mc3).
- Isolation and nucleotide sequencing of complementary DNA (cDNA) for pulmonary P-450MC.
Main Results:
- Cytochrome P-450MC was successfully induced in rat pulmonary microsomes by 3-methylcholanthrene and to a lesser extent by isosafrole.
- Cytochrome P-450d was not detected in rat lungs under the tested conditions using Western blot or Northern hybridization.
- The nucleotide sequence of pulmonary P-450MC cDNA showed no gross alterations when compared to the reported sequence of hepatic P-450c cDNA.
Conclusions:
- 3-methylcholanthrene is an effective inducer of Cytochrome P-450MC in rat lungs.
- Rat lungs do not appear to express detectable levels of Cytochrome P-450d under these experimental conditions.
- Pulmonary P-450MC is highly similar, if not identical, to hepatic P-450c at the nucleotide sequence level.