Identification of the cytochrome P-450 induced by macrolide antibiotics in rat liver as the glucocorticoid responsive cytochrome P-450p

• Published in: Biochemistry (Easton) 1985-04, Vol.24 (9), p.2171-2178
• Main Authors: Wrighton, Steven A, Maurel, Patrick, Schuetz, Erin G, Watkins, Paul B, Young, Beverly, Guzelian, Philip S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Anti-Bacterial Agents - pharmacology; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Biological and medical sciences; Cytochrome P-450 Enzyme System - biosynthesis; Electrophoresis, Polyacrylamide Gel; Enzyme Induction; Female; Immunosorbent Techniques; Isoenzymes - analysis; Liver - drug effects; Liver - enzymology; Male; Medical sciences; Microsomes, Liver - enzymology; Pharmacology. Drug treatments; Phenobarbital - pharmacology; Rats; Rats, Inbred Strains; Sex Factors; Spectrophotometry; Troleandomycin - pharmacology
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00330a010

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.