Cytochrome P-450 polypeptides in pulmonary microsomes from rats

Area of Science:

• Biochemistry
• Molecular Biology
• Toxicology

Background:

• Pulmonary microsomes contain integral membrane proteins, including various cytochrome P-450 (P-450) isozymes.
• Understanding lung P-450 expression is crucial for assessing xenobiotic metabolism and potential drug-induced toxicity in the respiratory system.

Purpose of the Study:

• To characterize pulmonary microsomal polypeptides, focusing on cytochrome P-450 (P-450) isozymes.
• To compare the expression profiles of pulmonary and hepatic microsomal proteins, particularly P-450s.

Main Methods:

• Two-dimensional electrophoresis was used to resolve pulmonary microsomal polypeptides.
• Triton X-114 detergent separation enriched for P-450s and integral membrane proteins.
• In situ peptide mapping further characterized the identified proteins.

Main Results:

• Cytochrome P-450b (P-450b) and epoxide hydrolase were detected in rat pulmonary microsomes, independent of phenobarbital treatment.
• Cytochrome P-450e (P-450e), typically co-induced with P-450b in the liver, was notably absent in pulmonary microsomes.
• Four additional pulmonary microsomal polypeptides were identified, with preliminary data suggesting three are unique P-450 isozymes related to P-450b.

Conclusions:

• Rat lungs express specific cytochrome P-450 (P-450) isozymes, including P-450b, which are distinct from hepatic expression patterns.
• The absence of P-450e in pulmonary microsomes suggests tissue-specific regulation of P-450 gene expression.
• Pulmonary microsomes may contain unique P-450 isozymes involved in lung-specific metabolic processes.