Transport of citrate across the brush border and basolateral membrane of rat small intestine
Identifieur interne : 001301 ( Main/Exploration ); précédent : 001300; suivant : 001302Transport of citrate across the brush border and basolateral membrane of rat small intestine
Auteurs : Siegfried Wolffram [Suisse] ; Rene Untern Hrer [Suisse] ; Beat Grenacher [Suisse] ; Erwin Scharrer [Suisse]Source :
- Comparative Biochemistry and Physiology -- Part A: Physiology [ 0300-9629 ] ; 1994.
Abstract
It was the aim of the present study to investigate the transport of tricarboxylates (citrate, tricarballylate) across the basolateral membrane (BLM) of the small intestine. Experiments were performed using BLM vesicles isolated from the jejunum of rats. For comparison, some experiments with brush border membrane (BBM) vesicles were also performed. Finally, transfer of citrate and tricarballylate across the intestinal wall was investigated using sacs of everted small intestine. Uptake of citrate by BBM vesicles occurs by a Na+ gradient-driven transport mechanism specific for tri- and dicarboxylates. The partially protonated forms of citrate seem to be much better transported than the completely dissociated form, since lowering the extravesicular pH from 7.8 to 5.6 resulted in a marked stimulation of Na+-dependent citrate uptake. In contrast to citrate uptake across the BBM, uptake of citrate across the BLM was neither influenced by Na2+ nor by pH changes. Neither structurally related tri- and dicarboxylates (tricarballylate, succinate) nor other organic and inorganic anions (e.g. lactate, P-aminohippurate, sulfate, chloride, bicarbonate) significantly influenced citrate uptake by BLM vesicles under cis-conditions. Uptake of citrate as a function of the extravesicular substrate concentration was linear over a concentration range from 0.1 to 10mmol/l. Thus, citrate uptake under these conditions seems to be Na+-independent and not to be mediated by a carrier. However, preloading the BLM V with citrate clearly mi/is-stimulated the uptake of citrate and tricarballylate, respectively. Furthermore, citrate significantly inhibited tricarballylate uptake into BLMV preloaded with citrate. These results indicate uptake of tricarboxylates across the BLM by an exchange mechanism. Using sacs of everted small intestine, no transfer of intact citrate against a concentration gradient occurred, but some evidence for metabolization of citrate within the intestinal wall was obtained. In contrast, the non-metabolizable tricarboxylate tricarballylate was significantly accumulated in the serosal compartment of everted intestinal sacs.
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DOI: 10.1016/0300-9629(94)90310-7
Affiliations:
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Zurich</region></placeName></affiliation></author></analytic><monogr></monogr><series><title level="j">Comparative Biochemistry and Physiology -- Part A: Physiology</title><title level="j" type="abbrev">CBAOLD</title><idno type="ISSN">0300-9629</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1994">1994</date><biblScope unit="volume">109</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="39">39</biblScope><biblScope unit="page" to="52">52</biblScope></imprint><idno type="ISSN">0300-9629</idno></series><idno type="istex">C76DF78487EE295CAE0801928A641DFDF87563BF</idno><idno type="DOI">10.1016/0300-9629(94)90310-7</idno><idno type="PII">0300-9629(94)90310-7</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0300-9629</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">It was the aim of the present study to investigate the transport of tricarboxylates (citrate, tricarballylate) across the basolateral membrane (BLM) of the small intestine. Experiments were performed using BLM vesicles isolated from the jejunum of rats. For comparison, some experiments with brush border membrane (BBM) vesicles were also performed. Finally, transfer of citrate and tricarballylate across the intestinal wall was investigated using sacs of everted small intestine. Uptake of citrate by BBM vesicles occurs by a Na+ gradient-driven transport mechanism specific for tri- and dicarboxylates. The partially protonated forms of citrate seem to be much better transported than the completely dissociated form, since lowering the extravesicular pH from 7.8 to 5.6 resulted in a marked stimulation of Na+-dependent citrate uptake. In contrast to citrate uptake across the BBM, uptake of citrate across the BLM was neither influenced by Na2+ nor by pH changes. Neither structurally related tri- and dicarboxylates (tricarballylate, succinate) nor other organic and inorganic anions (e.g. lactate, P-aminohippurate, sulfate, chloride, bicarbonate) significantly influenced citrate uptake by BLM vesicles under cis-conditions. Uptake of citrate as a function of the extravesicular substrate concentration was linear over a concentration range from 0.1 to 10mmol/l. Thus, citrate uptake under these conditions seems to be Na+-independent and not to be mediated by a carrier. However, preloading the BLM V with citrate clearly mi/is-stimulated the uptake of citrate and tricarballylate, respectively. Furthermore, citrate significantly inhibited tricarballylate uptake into BLMV preloaded with citrate. These results indicate uptake of tricarboxylates across the BLM by an exchange mechanism. Using sacs of everted small intestine, no transfer of intact citrate against a concentration gradient occurred, but some evidence for metabolization of citrate within the intestinal wall was obtained. In contrast, the non-metabolizable tricarboxylate tricarballylate was significantly accumulated in the serosal compartment of everted intestinal sacs.</div></front></TEI><affiliations><list><country><li>Suisse</li></country><region><li>Canton de Zurich</li></region><settlement><li>Zurich</li></settlement><orgName><li>Université de Zurich</li></orgName></list><tree><country name="Suisse"><region name="Canton de Zurich"><name sortKey="Wolffram, Siegfried" sort="Wolffram, Siegfried" uniqKey="Wolffram S" first="Siegfried" last="Wolffram">Siegfried Wolffram</name></region><name sortKey="Grenacher, Beat" sort="Grenacher, Beat" uniqKey="Grenacher B" first="Beat" last="Grenacher">Beat Grenacher</name><name sortKey="Scharrer, Erwin" sort="Scharrer, Erwin" uniqKey="Scharrer E" first="Erwin" last="Scharrer">Erwin Scharrer</name><name sortKey="Untern Hrer, Rene" sort="Untern Hrer, Rene" uniqKey="Untern Hrer R" first="Rene" last="Untern Hrer">Rene Untern Hrer</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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