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Bicarbonate sulfate exchange in canalicular rat liver plasma membrane vesicles

Meier, P. J. and Valantinas, J. and Hugentobler, G. and Rahm, I.. (1987) Bicarbonate sulfate exchange in canalicular rat liver plasma membrane vesicles. American journal of physiology. Gastrointestinal and liver physiology, Vol. 253, H. 4 , G461-G468.

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Official URL: http://edoc.unibas.ch/dok/A5261795

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Abstract

The mechanism(s) and driving forces for biliary excretion of sulfate were investigated in canalicular rat liver plasma membrane vesicles (cLPM). Incubation of cLPM vesicles in the presence of an inside-to-outside (in, out) bicarbonate gradient (50 mM in, 5 mM out, pH 8.0 in and out), but not pH (pH 8.0 in, 6.0 out) or out-to-in sodium gradients, stimulated sulfate uptake 10-fold compared with the absence of bicarbonate and approximately 2-fold above sulfate equilibrium ("overshoot"). Initial rates of this bicarbonate gradient-driven sulfate uptake were saturable with increasing concentrations of sulfate (apparent Km, approximately 0.3 mM) and could be inhibited by probenecid, N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate, acetazolamide, furosemide,4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (IC50, approximately 40 microM). Cisinhibition of initial bicarbonate gradient-stimulated sulfate uptake and transstimulation of sulfate uptake in the absence of bicarbonate were observed with sulfate, thiosulfate, and oxalate but not with chloride, nitrate, phosphate, acetate, lactate, glutamate, aspartate, cholate, taurocholate, dehydrocholate, taurodehydrocholate, and reduced or oxidized glutathione. These findings indicate the presence of a sulfate (oxalate)-bicarbonate anion exchange system in canalicular rat liver plasma membranes. In conjunction with the previously reported chloride-bicarbonate exchanger (J. Clin. Invest. 75: 1256-1263, 1985), these findings support the concept that bicarbonate-sensitive transport system might play an important role in bile acid-independent canalicular bile formation.
Faculties and Departments:11 Rektorat und Verwaltung > Vizerektorat Forschung
UniBasel Contributors:Meier-Abt, Peter J.
Item Type:Article, refereed
Bibsysno:Link to catalogue
Publisher:American Physiological Society
ISSN:0002-9513
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:22 Mar 2012 14:21
Deposited On:22 Mar 2012 13:23

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