Immunological identification and effects of 3-methylcholanthrene and phenobarbital on rat pulmonary cytochrome P-450.
Rabbit antibodies to the phenobarbital (PB) inducible rat liver microsomal cytochrome P-450s b and e and to 3-methylcholanthrene (MC) inducible P-450c were used to examine the expression of these isozymes in rat lungs. Western blots of total lung microsomes demonstrated that about 40 pmol P-450b/mg protein (and no detectable P-450e) were present in lungs from control or MC treated rats and that pretreatment with PB caused a small but significant (P less than 0.05) increase in the expression of P-450b. Microsomes from control and PB treated lung contained minimal levels of P-450c, and MC induced this isozyme to 185 pmol/mg. Immunocytochemistry was used to demonstrate immunoreactivity to these isozymes in specific cell types. Neither P-450b nor P-450c was detectable in endothelial cells from control or PB treated lungs, but MC increased immunoreactivity to P-450c in pulmonary endothelial cells. Type II alveolar cells showed distinct immunoreactivity to P-450b and weak immunoreactivity to P-450c in control or PB treated rats. Individual Clara cells stained for either P-450c or P-450b in control, MC treated, and PB treated rats, and colocalization was observed in some cells. An increase in type II alveolar cell and Clara cell immunoreactivity to P-450c was observed after MC induction. Mast cells, identified by metachromatic Giemsa staining, appeared to react nonspecifically with both antisera. In conclusion, P-450c is highly inducible by MC in rat lung (detected in microsomes by Western blot), specifically in endothelial cells, Clara cells, and alveolar type II cells (as visualized by immunocytochemistry); and P-450b is present in rat lung microsomes, and immunoreactivity to this isozyme is localized in alveolar type II and Clara cells.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004790:Enzyme Induction; D007124:Immunoenzyme Techniques; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D010634:Phenobarbital