Na+-dependent and -independent Cl−/HCO exchange mediate cellular HCO transport in cultured human intrahepatic bile duct cells

✍ Scribed by M Strazzabosco; R Joplin; A Zsembery; L Wallace; C Spirli; L Fabris; A Granato; A Rossanese; C Poci; J M Neuberger; L Okolicsanyi; G Crepaldi

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 285 KB
• Volume: 25
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.510250431

✦ Synopsis

able. Administration of agents raising intracellular Biliary epithelial cells (cholangiocytes) modulate bile cAMP concentrations increased both Na / -dependent fluidity and alkalinity absorbing and/or secreting fluid and Na / -independent Cl 0 /HCO 0 3 exchange activity. Stimand electrolytes, particularly HCO 0 3 and Cl 0 . Mechaulation of Cl 0 /HCO 0 3 exchange activity was not prenisms responsible for transepithelial H / /HCO 0 3 secretion vented by the Cl 0 channel inhibitor 5-nitro-2(2)-phein human cholangiocytes are largely unknown. Human nylpropyl-amino-benzoate(NPPB). In conclusion, hucholangiocytes isolated by enzymatic digestion and imman cholangiocytes possess two acid extruders (Na / /H / munomagnetic purification from normal liver tissue obexchanger and Na / -dependent Cl 0 /HCO 0 3 exchange) and tained from reduced grafts used for pediatric liver transan acid loader (Cl 0 /HCO 0 3 exchange), whereas no eviplantation were cultured in the presence of human dence was found for cAMP activated H / -ATPase. Bicarhepatocyte growth factor. Maintenance of cholangiocyte bonate influx is thus mainly mediated by Na-dependent phenotypic features was assessed using markers such Cl 0 /HCO 0 3 exchange, whereas Na / :HCO 0 3 cotransport is as cytokeratin 19, g-glutamyltranspeptidase, vimentin, not active in the physiological range of pHi. Stimulation factor VIII-related antigen, desmin, epithelial memof Na / -independent Cl 0 /HCO 0 3 exchanger by cAMP does brane antigen (EMA), and human epithelial antigen not require activation of Cl 0 conductances. These mech-(HEA) 125. Intracellular pH (pHi) transients were meaanisms may underlay hormone-regulated biliary HCO 0 3 sured microfluorimetrically 27-Bis(2-carboxyethyl)-5,6, secretion in the human biliary tree. (HEPATOLOGY carboxyfluorescein-acetossimethylester (BCECF). In 1997;25:976-985.) the absence of HCO 0 3 , pHi recovery from an intracellular acid load (ammonia pre-pulse technique) was Na / -dependent and amiloride-inhibitable. No Na / -independent

Interest in cholangiocyte physiology and pathophysiology recovery was recorded even after stimulation with has been stimulated by the observation that the biliary epiagents raising intracellular cyclic adenosine monophosthelium is the primary target in several chronic cholestatic phate (cAMP) concentrations. In the presence of liver disorders, including primary biliary cirrhosis, primary HCO 0 3 , recovery from an intracellular acid load required sclerosing cholangitis, and liver allograft rejection. [1][2][3][4][5] Inter-Na / , but was only partly inhibited by amiloride. In these estingly, in cystic fibrosis, a disease of ion transporting epiconditions H / extrusion was inhibited by 4,4,-diisothiothelia, hepatobiliary complications occur in approximately cyan atostilben-2,2,-disulfonic acid (DIDS) and by intra-30% of cases 6 and ultrastructural bile duct cell damage can cellular Cl 0 depletion. Acute removal of extracellular Cl 0 be shown well before hepatocellular damage. 7 In this condiinduced a pHi alkalinization that was inhibited by DIDS. tion, low rates of ductular HCO 0 3 and Cl 0 secretion may lead pHi recovery from an intracellular alkaline load (isohyto increased viscosity of bile and ''ductular'' cholestasis. 7,8 dric CO 2 changes) was Cl 0 -dependent and DIDS-inhibit-Hepatocellular bile is, in fact, extensively modified while flowing through the biliary tree. The epithelial cells lining the intrahepatic bile ducts (cholangiocytes) modulate bile fluidity Abbreviations: cAMP, cyclic adenosine monophosphate; NPPB, 5-nitro-2(2)-phenylproand alkalinity absorbing or secreting fluid and electrolytes, pyl-amino-benzoate; Hepes, N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid; DIDS, 4,4,-diisothiocyanatostilben-2,2,-disulfonic acid; DBcAMP, N 6 ,2-O-dibutyryladenosine particularly HCO 0 3 and Cl 0 , under the influence of digestive 3:5-cyclic monophosphate; IBMX, 3-isobutyl-1-methyl-xanthine; BCECF-AM, 2:7-Bis(2-hormones such as secretin and somatostatin. 1,3-5,9,10 Studies carboxyethyl)-5,6, carboxyfluorescein-acetossimethylester; HEA, human epithelial antigen;

in short-term cultured intrahepatic rat cholangiocytes have g-GT, g-glutamyltranspeptidase; pHi, intracellular measurements; Bi, intrinsic buffering characterized a number of membrane carriers and ion chanpower; KRB, bicarbonate buffered ringer.