Regulation of the rabbit cytochrome P-450 3c gene. Age-dependent expression and transcriptional activation by rifampicin.
The macrolide antibiotic rifampicin is a potent inducer of cytochrome P-450-mediated drug metabolism in humans and rabbits. In this report, we demonstrate that in immature rabbits, rifampicin activates the transcription of the Cyp3A6 gene which encodes P450IIIA6 (cytochrome P-450 3c). The maximum increase in transcription was seen at 12 h following administration of rifampicin. Northern and slot blot analyses indicate that mRNAs corresponding to P450IIIA6 accumulates during the period of increased transcription and persist at 18 h when the rate of transcription has returned to basal levels. P450IIIA6 protein accumulates in liver microsomes over this period. At 24 h a greater than 10-fold increase in microsomal P450IIIA6 protein is detected by immunoblotting using a monoclonal antibody to P450IIIA6. The rate of microsomal progesterone 6 beta-hydroxylase activity is also elevated when compared to untreated rabbits, and this enzyme is activated in vitro by alpha-naphthoflavone. To determine whether this enzyme is stimulated by alpha-naphthoflavone in intact cells, COS-1 cells were transfected with an expression vector harboring the coding region of a P450IIIA6 cDNA. Our results demonstrate that the transfected COS-1 cells exhibit progesterone 6 beta-hydroxylase activity that is stimulated by alpha-naphthoflavone added to the culture medium.
Department of Medicine, University of California, San Diego, La Jolla 92093.
C L
CL
Potenza
U R
UR
Pendurthi
D K
DK
Strom
R H
RH
Tukey
K J
KJ
Griffin
G E
GE
Schwab
E F
EF
Johnson
D000375:Aging; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005786:Gene Expression Regulation / Q000187:drug effects*; D005796:Genes / Q000187:drug effects*; D008099:Liver / Q000254:growth & development*; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D011817:Rabbits; D015183:Restriction Mapping; D012293:Rifampin / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
D000911:Antibodies, Monoclonal; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D012293:Rifampin