P-glycoprotein function and expression during obstructive cholestasis in rats.
OBJECTIVE
The present study was aimed at evaluation of in vivo biliary and renal excretion of rhodamine 123 (Rho123), a P-glycoprotein (P-gp) substrate, in rats during either acute or chronic cholestasis induced by bile duct obstruction (BDO).


METHODS
The Rho123 clearance study was performed either one (BDO1) or seven (BDO7) days after BDO. Bile flow was reconstituted, and bile and urine were collected after steady-state plasma concentration of Rho123 was attained. Tissue expression of P-gp was evaluated by quantitative immunohistochemistry, and immunoblotting.


RESULTS
Significant up-regulation of the liver P-gp protein was observed in acute and chronic cholestasis. Primary periportal location of P-gp was enlarged also to pericentral areas. In the kidneys, immunohistochemistry showed pancellular increase in P-gp after 1 day of BDO, which subsided after 7 days of BDO. Nevertheless, biliary and renal clearances (CL(Bile) and CL(R)) of Rho123 did not reflect the induction of P-gp expression. While CL(Bile) was reduced one day after cholestasis and restored on the seventh day, the CL(R) was preserved in BDO1 group and reduced in BDO7 group without change in glomerular filtration rate. In parallel, biliary and renal clearances of conjugated bilirubin were significantly reduced in both cholestatic groups compared with controls.


CONCLUSIONS
These findings suggest that extrahepatic cholestasis causes time-dependent changes in elimination of Rho123 which do not exactly reflect alteration of P-gp expression in the rat liver and kidney. These data may help to explain impaired elimination of P-gp substrates after short-term cholestasis that may commonly occur in clinical practice.
Micuda
Stanislav
S
Department of Pharmacology, Faculty of Medicine in Hradec Kralove, Charles University in Prague, Hradec Kralove, The Czech Republic. micuda@lfhk.cuni.cz
Brcakova
Eva
E
Fuksa
Leos
L
Cermanova
Jolana
J
Osterreicher
Jan
J
Hroch
Milos
M
Mokry
Jaroslav
J
Pejchal
Jaroslav
J
Martinkova
Jirina
J
Staud
Frantisek
F
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism / Q000502:physiology*; D000208:Acute Disease; D000818:Animals; D001646:Bile / Q000378:metabolism; D001663:Bilirubin / Q000378:metabolism; D015153:Blotting, Western; D001651:Cholestasis, Extrahepatic / Q000209:etiology / Q000378:metabolism*; D002908:Chronic Disease; D004195:Disease Models, Animal; D005456:Fluorescent Dyes; D007668:Kidney / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D020112:Rhodamine 123
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005456:Fluorescent Dyes; D020112:Rhodamine 123; D001663:Bilirubin