We investigated the transport systems that can sustain Na+ and Cl- movements across bovine gall bladder epithelium, focusing on the Na+-H+ exchanger (NHE) family and chloride conductive pathways. Experiments conducted using the fluorescent probe acridine orange (AO) with brush-border membrane vesicles (BBMV) or vesicles obtained from the total epithelium (EMV) demonstrated the presence of a Na+-H+ exchange in both preparations. The use of specific inhibitors indicated the presence of an apical NHE3 exchanger and a NHE1 isoform which should reside in the basolateral membrane. Using reverse transcriptase (RT) PCR, we identified cDNA fragments corresponding to the NHE1, NHE3, Cl--HCO3- (AE2a) transporters and to the CFTR channel. Using the patch-clamp technique, we investigated Cl- conductances on cultured epithelial cells. We found a 5 pS Cl- channel with a voltage-independent open probability, insensitive to stilbenes (SITS), Zn2+ and cAMP. The results suggest that absorption and secretion coexist in calf gall bladder epithelium. A Na+-H+-Cl--HCO3- double exchange may, at least partially, sustain the absorptive function, and a Cl- apical conductive pathway may be involved in secretion. The conductance we observed does not seem to be cAMP-regulated, unlike other mammalian gall bladders.
The presence of NHE1 and NHE3 Na+-H+ exchangers and an apical cAMP-independent Cl- channel indicate that both absorptive and secretory functions are present in calf gall bladder epithelium / C. Bazzini, G. Bottà, G. Meyer, M.D. Baroni, M. Paulmichl. - In: EXPERIMENTAL PHYSIOLOGY. - ISSN 0958-0670. - 86:5(2001), pp. 571-583.
The presence of NHE1 and NHE3 Na+-H+ exchangers and an apical cAMP-independent Cl- channel indicate that both absorptive and secretory functions are present in calf gall bladder epithelium
C. BazziniPrimo
;G. BottàSecondo
;G. Meyer;M.D. Baroni;M. PaulmichlUltimo
2001
Abstract
We investigated the transport systems that can sustain Na+ and Cl- movements across bovine gall bladder epithelium, focusing on the Na+-H+ exchanger (NHE) family and chloride conductive pathways. Experiments conducted using the fluorescent probe acridine orange (AO) with brush-border membrane vesicles (BBMV) or vesicles obtained from the total epithelium (EMV) demonstrated the presence of a Na+-H+ exchange in both preparations. The use of specific inhibitors indicated the presence of an apical NHE3 exchanger and a NHE1 isoform which should reside in the basolateral membrane. Using reverse transcriptase (RT) PCR, we identified cDNA fragments corresponding to the NHE1, NHE3, Cl--HCO3- (AE2a) transporters and to the CFTR channel. Using the patch-clamp technique, we investigated Cl- conductances on cultured epithelial cells. We found a 5 pS Cl- channel with a voltage-independent open probability, insensitive to stilbenes (SITS), Zn2+ and cAMP. The results suggest that absorption and secretion coexist in calf gall bladder epithelium. A Na+-H+-Cl--HCO3- double exchange may, at least partially, sustain the absorptive function, and a Cl- apical conductive pathway may be involved in secretion. The conductance we observed does not seem to be cAMP-regulated, unlike other mammalian gall bladders.Pubblicazioni consigliate
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