title: Identification of the cytochrome P-450 induced by macrolide antibiotics in rat liver as the glucocorticoid responsive cytochrome P-450p.
abstract: We administered triacetyloleandomycin (TAO) to rats and found that this macrolide antibiotic is the most efficacious inducer of liver microsomal cytochrome P-450 (P-450) examined to date. Liver microsomes prepared from TAO-treated rats contained greater than 5.0 nmol of P-450/mg of protein and a single induced protein as judged by analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein comigrated with P-450p, the major form of P-450 induced in liver microsomes of rats treated with pregnenolone-16 alpha-carbonitrile (PCN) or dexamethasone (DEX). On immunoblots of such gels developed with antibodies to P-450p, the TAO-induced protein reacted strongly as a single band. There was strict parallelism between the amount of immunoreactive P-450p in liver microsomes prepared from untreated rats or from rats treated with phenobarbital, TAO, DEX, or PCN, the ability of these microsomes to catalyze conversion of TAO to a metabolite which forms a spectral complex, and the ethylmorphine and erythromycin demethylase activities. Antibodies to P-450p specifically blocked microsomal TAO metabolite complex formation and ethylmorphine and erythromycin demethylase activities. Moreover, anti-P-450p antibodies completely immunoprecipitated solubilized TAO metabolite complexes prepared by detergent treatment of liver microsomes obtained from TAO-treated rats. Finally, we found that the major form of P-450 isolated from liver microsomes of TAO-treated rats and purified to homogeneity was indistinguishable from purified P-450p as judged by molecular weights, spectral characteristics, enzymatic activities, ability to bind TAO, peptide maps, and amino-terminal amino acid sequences. We concluded that, in addition to glucocorticoids, macrolide antibiotics are specific inducers of P-450p.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D005260:Female; D007163:Immunosorbent Techniques; D007527:Isoenzymes / Q000032:analysis; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013053:Spectrophotometry; D014217:Troleandomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D010634:Phenobarbital