Intracellular alkalinization stimulates bile flow and vesicular-mediated exocytosis in IPRL.
Intracellular pH recovery from an acute alkaline load in rat hepatocytes is mediated by a Cl(-)-HCO3- exchanger, which is electroneutral, Na+ independent, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) sensitive. Stimulation of this Cl(-)-HCO3- exchanger requires intact microtubules, suggesting that vesicular transport may be required to activate this exchanger. To determine if intracellular alkalinization stimulates biliary HCO3- excretion and bile flow in the intact liver by vesicle-mediated exocytosis, isolated perfused rat livers (IPRL) were alkalinized by two protocols. Isohydric changes in CO2 and HCO3- concentrations induced transient increases in bile flow by 36% (P < 0.01), which were abolished by DIDS (0.01 mM), inhibited by pretreatment with colchicine (P = 0.01), but not affected by membrane depolarization with the K(+)-channel blocker BaCl2 (1 mM). Similarly, perfusion with 20 mM NH4Cl produced a 42% increase in bile flow (P < 0.01) and a 26% increase in biliary HCO3- excretion. Both the increases in bile flow and HCO3- excretion were almost completely blocked by DIDS and inhibited by pretreatment with colchicine (P < 0.01). Biliary excretion of horseradish peroxidase was also increased during intracellular alkalinization with either protocol (P < 0.01). These findings suggest that intracellular alkalinization stimulates bile flow and biliary HCO3- excretion. Microtubule-dependent vesicular-mediated exocytosis is involved in this response.
Bruck
R
R
Liver Center, Yale University, School of Medicine, New Haven, Connecticut 06510.
Benedetti
A
A
Strazzabosco
M
M
Boyer
J L
JL
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000468:Alkalies / Q000378:metabolism*; D000818:Animals; D000838:Anions / Q000037:antagonists & inhibitors / Q000378:metabolism; D001464:Barium / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism; D001646:Bile / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D005089:Exocytosis; D006735:Horseradish Peroxidase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D000468:Alkalies; D000838:Anions; D001639:Bicarbonates; D015221:Potassium Channels; D001464:Barium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D006735:Horseradish Peroxidase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D003078:Colchicine