title: Vesicle targeting to the apical domain regulates bile excretory function in isolated rat hepatocyte couplets.
abstract: OBJECTIVE
  Plasma membrane solute transport may be regulated in many epithelial cells by vesicle traffic to and from the site of residence of the transporter. The aim of this study was to determine if this phenomenon may also play a role in the regulation of canalicular transport of bile acids.
  
  
  METHODS
  Confocal microscopy and image analysis were performed to quantitatively assess changes in secretory capacity and vesicle targeting in isolated rat hepatocyte couplets that had been exposed to fluorescent bile acid after pretreatment with dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) and/or nocodazole.
  
  
  RESULTS
  DBcAMP stimulated bile acid secretion by 240% while significantly increasing canalicular circumference. Nocodazole decreased secretion by 410% and significantly decreased canalicular circumference. When DBcAMP was added to nocodazole-treated couplets, a slight but significant increase was found in both fluorescent bile acid secretion and canalicular circumference as compared with nocodazole alone. Finally, DBcAMP stimulated translocation of vesicles to the canalicular membrane as determined by immunocytochemical localization of a putative bile acid transporter, Ca2+, Mg2+-ecto-adenosine triphosphatase.
  
  
  CONCLUSIONS
  The findings support the view that apical membrane transport activity in the rat hepatocyte is highly regulated by the insertion of vesicles into this domain and that this process involves both microtubule-dependent and -independent mechanisms.
authors.affiliation: Department of Medicine and Liver Center, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Boyer
authors.forename: C J
authors.initials: CJ
authors.lastname: Soroka
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D001648:Bile Canaliculi / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002478:Cells, Cultured; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D018613:Microscopy, Confocal; D008870:Microtubules / Q000502:physiology; D015739:Nocodazole / Q000494:pharmacology; D051381:Rats
chemical_list: D001647:Bile Acids and Salts; D003994:Bucladesine; D017301:Ca(2+) Mg(2+)-ATPase; D015739:Nocodazole