title: Regulation of activity and apical targeting of the Cl-/HCO3- exchanger in rat hepatocytes.
abstract: To test the hypothesis that rat hepatocyte canalicular Cl-/HCO3- exchange activity might be regulated by HCO3- or protein kinase-induced changes in the apical targeting of vesicles, isolated rat hepatocytes were cultured in the presence or absence of HCO3-/CO2.Cl-/HCO3- exchange activity increased in cells cultured in the presence of HCO3-/CO2 or when stimulated by dibutyryl cAMP. Both of these effects were blocked by either colchicine or the protein kinase C agonist phorbol 12,13-dibutyrate. Fluorescence and confocal microscopy, respectively, revealed increased pericanalicular-apical membrane localization of two canalicular markers, peanut agglutinin and a 110-kDa canalicular ecto-ATPase, when hepatocyte couplets were preincubated in HCO3-/CO2-containing medium, an effect that was again blocked by colchicine. Dibutyryl cAMP also stimulated canalicular localization of the 110-kDa protein. These findings suggest that hepatocyte Cl-/HCO3- exchange activity is regulated by HCO3-/CO2 and by protein kinase A and protein kinase C agonists through microtubule-dependent targeting of vesicles containing this exchanger to the canalicular domain.
authors.affiliation: Department of Internal Medicine and Liver Center, Yale University, School of Medicine, New Haven, CT 06510.
authors.forename: A
authors.initials: A
authors.lastname: Benedetti
authors.forename: M
authors.initials: M
authors.lastname: Strazzabosco
authors.forename: O C
authors.initials: OC
authors.lastname: Ng
authors.forename: J L
authors.initials: JL
authors.lastname: Boyer
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D017920:Antiporters / Q000187:drug effects / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D017136:Ion Transport; D037102:Lectins / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D019887:Peanut Agglutinin; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D051381:Rats
chemical_list: D017920:Antiporters; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D037102:Lectins; D019887:Peanut Agglutinin; D015240:Phorbol 12,13-Dibutyrate; D003994:Bucladesine; D000242:Cyclic AMP; D000251:Adenosine Triphosphatases; C027201:ectoATPase