Regulation by dexamethasone of P-glycoprotein expression in cultured rat hepatocytes.
We have examined P-glycoprotein (P-gp) expression and function in cultured rat hepatocytes in response to dexamethasone (DEX), which is known to modulate various liver functions. Northern blot analyses revealed high levels of P-gp mRNAs in cultured untreated liver cells in comparison to those found in freshly isolated hepatocytes, while DEX-treated hepatocytes also displayed elevated, although weaker, P-gp levels. Similarly, Western blotting analysis indicated high levels of P-gp in liver cells maintained in the absence of DEX. The use of mdr gene-specific probes allowed us to show that DEX-modulated P-gp induction in cultured hepatocytes involved mostly, if not specifically, mdr1 gene regulation. Doxorubicin P-gp-mediated efflux analyses revealed lower intracellular doxorubicin accumulation in DEX-untreated liver cells than in DEX-treated cells, thus indicating that over-expressed P-gp was functional. These data clearly show that DEX treatment strongly modulates P-gp expression in primary rat hepatocyte cultures through a specific effect on the mdr1 gene.
Fardel
O
O
INSERM U 49, Unité de recherches Hépatologiques, Hôpital Pontchaillou, Rennes, France.
Lecureur
V
V
Guillouzo
A
A
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004317:Doxorubicin / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000187:drug effects*; D015151:Immunoblotting; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D003907:Dexamethasone; D004317:Doxorubicin; D014700:Verapamil