Alterations in vesicle transport and cell polarity in rat hepatocytes subjected to mechanical or chemical cholestasis.
OBJECTIVE
The molecular mechanisms that contribute to the cholestatic condition in hepatocytes are poorly defined. It has been postulated that a disruption of normal vesicle-based protein trafficking may lead to alterations in hepatocyte polarity.


METHODS
To determine if vesicle motility is reduced by cholestasis, hepatocytes cultured from livers of bile duct ligation (BDL)- or ethinyl estradiol (EE)-injected rats, were viewed and recorded by high-resolution video microscopy. Cholestatic hepatocytes were analyzed by phalloidin staining and electron microscopy. Functional analysis was done by the sodium fluorescein sequestration assay.


RESULTS
In cholestatic hepatocytes, there was a significant decrease in the number of motile cytoplasmic vesicles observed compared with control cells. Further examination of cells from BDL- or EE-treated livers revealed the presence of numerous large intracellular lumina. More than 24% of cells in BDL-treated livers and 19% of cells in EE-treated livers displayed these structures, compared with 1.1% found in control hepatocytes. Phalloidin staining of hepatocytes showed a prominent sheath of actin surrounding the lumina, reminiscent of those seen about bile canaliculi. Electron microscopy revealed that these structures were lined by actin-filled microvilli. Further, these pseudocanaliculi perform many of the functions exhibited by bona fide canaliculi, such as sequestering sodium fluorescein.


CONCLUSIONS
Both mechanically and chemically induced cholestasis have substantial effects on vesicle-based transport, leading to marked disruption of hepatocellular polarity.
Török
N J
NJ
Center for Basic Research in Digestive Diseases, Mayo Clinic, Rochester, Minnesota 55905, USA.
Larusso
E M
EM
McNiven
M A
MA
D000818:Animals; D001648:Bile Canaliculi / Q000502:physiology; D001692:Biological Transport; D018929:Cell Culture Techniques; D016764:Cell Polarity; D002779:Cholestasis / Q000473:pathology*; D022162:Cytoplasmic Vesicles / Q000502:physiology*; D022781:Hepatocytes / Q000502:physiology* / Q000648:ultrastructure*; D008854:Microscopy, Electron; D051381:Rats; D011916:Rats, Inbred F344