Basolateral Cl-/HCO3- exchange in rat jejunum: evidence from H14CO3- uptake in membrane vesicles.
Bicarbonate transport across basolateral membrane vesicles from rat jejunal enterocyte was studied at 28 degrees C and pH 8.2. These experimental conditions make possible the determination of [14C]bicarbonate uptake. Inward gradients of Na+, K+, and Li+ did not stimulate HCO3- uptake, suggesting that a cotransport mechanism with these cations does not occur. On the contrary a countertransport of bicarbonate driven by a Cl- gradient was evidenced. The ability of other inorganic anions to exchange with HCO3- was examined and results indicate that Cl- can be substituted by NO3-, Br- and SCN-. The Cl(-)-dependent HCO3- uptake was strongly inhibited by SITS and DIDS, whereas acetazolamide was ineffective: thus transfer of labelled CO2 is eliminated as a possible mode of HCO3- permeation. HCO3- uptake was also affected by the presence of superimposed membrane potentials, suggesting that a HCO3- conductive pathway is present in the jejunal basolateral membrane. These results show that there are no fundamental differences between data obtained performing H14CO3- and 36Cl- (previously reported) uptake experiments.
Orsenigo
M N
MN
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
Tosco
M
M
Faelli
A
A
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium
D001639:Bicarbonates; D002412:Cations; D002712:Chlorides; D014316:Tritium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000086:Acetazolamide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid