Impaired localisation and transport function of canalicular Bsep in taurolithocholate induced cholestasis in the rat.
BACKGROUND
Taurolithocholate induced cholestasis is a well established model of drug induced cholestasis with potential clinical relevance. This compound impairs bile salt secretion by an as yet unclear mechanism.


OBJECTIVE
To evaluate which step/s of the hepatocellular bile salt transport are impaired by taurolithocholate, focusing on changes in localisation of the canalicular bile salt transporter, Bsep, as a potential pathomechanism.


METHODS
The steps in bile salt hepatic transport were evaluated in rats in vivo by performing pharmacokinetic analysis of (14)C taurocholate plasma disappearance. Bsep transport activity was determined by assessing secretion of (14)C taurocholate and cholyl-lysylfluorescein in vivo and in isolated rat hepatocyte couplets (IRHC), respectively. Localisation of Bsep and F-actin were assessed both in vivo and in IRHC by specific fluorescent staining.


RESULTS
In vivo pharmacokinetic studies revealed that taurolithocholate (3 micro mol/100 g body weight) diminished by 58% canalicular excretion and increased by 96% plasma reflux of (14)C taurocholate. Analysis of confocal images showed that taurolithocholate induced internalisation of Bsep into a cytosolic vesicular compartment, without affecting F-actin cytoskeletal organisation. These effects were reproduced in IRHC exposed to taurolithocholate (2.5 micro M). Preadministration of dibutyryl-cAMP, which counteracts taurolithocholate induced impairment in bile salt secretory function in IRHC, restored Bsep localisation in this model. Furthermore, when preadministered in vivo, dibutyryl-cAMP accelerated recovery of both bile flow and bile salt output, and improved by 106% the cumulative output of (14)C taurocholate.


CONCLUSIONS
Taurolithocholate impairs bile salt secretion at the canalicular level. Bsep internalisation may be a causal factor which can be prevented by dibutyryl-cAMP.
Crocenzi
F A
FA
Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET-UNR), Rosario, Argentina.
Mottino
A D
AD
Sánchez Pozzi
E J
EJ
Pellegrino
J M
JM
Rodríguez Garay
E A
EA
Milkiewicz
P
P
Vore
M
M
Coleman
R
R
Roma
M G
MG
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D001692:Biological Transport; D002756:Cholagogues and Choleretics / Q000037:antagonists & inhibitors* / Q000493:pharmacokinetics; D002779:Cholestasis / Q000139:chemically induced* / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013658:Taurolithocholic Acid / Q000009:adverse effects* / Q000493:pharmacokinetics
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; C490548:Abcb11 protein, rat; D000199:Actins; D001647:Bile Acids and Salts; D002756:Cholagogues and Choleretics; D013658:Taurolithocholic Acid