Chloride-bicarbonate exchange in the urinary bladder of the turtle. Independence from sodium ion

Husted, Russell F.; Eyman, E

doi:10.1016/0005-2736(80)90092-9

Cited by 10 publications

(3 citation statements)

References 10 publications

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“…This result is somewhat surprising, particularly with respect to HCO3 which has been implicated in anion exchange processes in a number of epithelial tissues. (For example: Amphiuma small intestine [34]; rat ileum [17]; human ileum [31]; turtle bladder [18,21]). Ullrich and coworkers [32] describe a HCO3-dependence of SOs reabsorption in the proximal convoluted tubule of rat kidney.…”

Section: Discussionmentioning

confidence: 99%

Sulfate transport in rabbit ileum: Characterization of the serosal border anion exchange process

Langridge-Smith

Field

1981

J. Membrain Biol.

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The preceding paper [30] shows that transepithelial ileal SO4 transport involves Na-dependent uptake across the ileal brush border, and Cl-dependent efflux across the serosal border. The present study examines more closely the serosal efflux process. Transepithelial mucosa (m)-to-serosa (s) and sto-m fluxes (Jms, Jsm) across rabbit ileal mucosa were determined under short-circuit conditions. SO4 was present at 0,22 mM. In standard C1, HCO3 Ringer's, jso4 was 81.3 +5.3 (1SE) and jso4 was 2.5_+0.2 nmol cm-2hr-l(n=20). Serosal addition of 4-acetamido-4'-isothiocyanostilbene-22'-disulfonate (SITS), 44'-diisothiocyanostilbene-22'-disulfonate (DIDS) or 1-anilino-8-naphthalene-sulfonate (ANS) inhibited SO4 transport, SITS being the most potent. Several other inhibitors of anion exchange in erythrocytes and other cells had no effect on ileal SO4 fluxes. In contrast to its effect on SO4 transport, SITS (500 gM) did not detectably alter C1 transport.Replacement of all C1, HCO3 and PO~ with gluconate reduced jso4 by 70% and increased jso4 by 400%. A small but significant I s~ remained, lso4 vnet ~ms could be increased by addition to the serosal side of C1, Br, I, NO3 or SO4. The stimulatory effect of all these anions was saturable and SITS-inhibitable. The maximal jso4 in the presence of C1 was considerably higher than in the presence of SO4 (73.1 and 42.2nmol cm -2 hr -t, respectively; p<0.001). The K~ value for C1 was 7.4 mM, 10-fold higher than that for SO4 (0.7 mM). Omitting HCO3 and PO4 had no measurable effects on SO4 fluxes.This study shows that (i) SO4 crosses the serosal border of rabbit ileal mucosa by anion exchange; (i 0 the exchange process is inhibited by SITS, DIDS and ANS, but not by several other inhibitors of anion exchange in other systems; (iii) SO4 may exchange for C1, Br, I, NO3 and SO4 itself, but probably not for HCO3 or PO~; (iv) kinetics of the exchange system suggest there is a greater affinity for SO4 than for C1, although the maximal rate of exchange is higher in the presence of C1; and, finally (v) SITS has little or no effect on net C1 transport.The preceding paper [30] shows that active SO4 absorption in rabbit ileum involves two separate steps: (0 a Na-dependent uptake at the brush border, and (ii) a Cl-dependent efflux at the serosal border. The latter can be blocked by the stilbene derivatives 4-acetamido-4'-isothiocyanostilbene-2,T-disulfonate (SITS) 1 and 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS), which are potent inhibitors of anion exchange in both erythrocytes [5] and Ehrlich ascites tumor cells [22,23]. In the present study, we further investigate the serosal border component of SO4 transport in rabbit ileum. Transepithelial mucosa (m)-to-serosa (s) and s-to-m fluxes of SO4 were determined under short-circuit conditions in Ringer's solutions of different anionic compositions. The effects of a number of anion transport inhibitors were also tested. For most flux measurements, the SO~ concentration was set at 0.22 mM, or about 10-fold lower than in the preceding study [30], ...

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Section: Discussionmentioning

confidence: 99%

Sulfate transport in rabbit ileum: Characterization of the serosal border anion exchange process

Langridge-Smith

Field

1981

J. Membrain Biol.

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“…shown that the isolated turtle bladder is capable of electroneutral HCO^ sécrétion (Jnco,) into the urinary compartment. Under ordinary conditions, the sécrétion of bicarbonate is coupled to Cl" absorption (12) but is independent of Na"^ transport (10,12). Furthermore, Husted et al (9) have suggested that the pathway for Jnco, is also separate from that of urinary acidification.…”

Section: Pre Vious Studie S By Leslie and Colleagues (12) Havementioning

confidence: 99%

A double-membrane model for urinary bicarbonate secretion

Stetson¹,

Beauwens²,

Palmisano³

et al. 1985

American Journal of Physiology-Renal Physiology

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To define the transport pathway for HCO-3 secretion (JHCO3) across the apical and basolateral membranes of turtle bladder, we examined the effects of cAMP, isobutylmethylxanthine (IBMX), the Cl- channel blocker 9-anthroic acid (9-AA), and the disulfonic stilbene DIDS (4,4'-diisothiocyanostilbene-2,2'-sulfonic acid) on the electroneutral and electrogenic components of JHCO3. Total JHCO3 was measured by pH stat titration of the mucosal compartment after Na+ absorption and H+ secretion were abolished by ouabain and a delta pH, respectively. Addition of cAMP or IBMX increased total JHCO3 and induced a short-circuit current (ISC), accounting for a large part of JHCO3; net Cl- absorption was reduced. Mucosal 9-AA inhibited the IBMX-induced electrogenic component of JHCO3, whereas mucosal DIDS inhibited the electroneutral component and acetazolamide reduced both. We suggest that HCO-3 is generated within the cell by a Na-independent primary active acid-base transport at the basolateral membrane (H+ extrusion into the serosal compartment). Cellular HCO-3 accumulation drives JHCO3 via a Cl-HCO3 exchanger at the luminal membrane. IBMX and cAMP activate a 9-AA-sensitive anion conductance parallel to the exchanger. The apparent reversal of the transport elements between the two cell membranes (compared with H+-secreting cells) led to an ultrastructural examination of the carbonic anhydrase-rich cells.

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“…When examined under rigorous in vitro conditions the movements of both ions are against their electrochemical gradients [1,3,5,17]. Moreover, although the exchange is independent of the presence of N a + in the medium bathing turtle urinary bladder [1,11] and rabbit colon [5], C t --H C O~ exchange in guinea pig gallbladder [9] is reported to be N a +-dependent.…”

Section: Introductionmentioning

confidence: 99%

Intestinal HCO 3 − secretion inAmphiuma: Stimulation by mucosal Cl− and serosal Na+

White

Imon

1982

J. Membrain Biol.

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The requirement for Na+ and Cl- in the bathing media to obtain a maximal HCO3- secretory flux (JHCO3-) across isolated short-circuited Amphiuma duodenum was investigated using titration techniques and ion substitution. Upon substitution of media Na+ with choline, HCO3- secretion was markedly reduced. Replacement of media Cl- produced a smaller reduction of JHCO3-. The presence of Cl- enhanced HCO3- secretion only if Na+ was also in the media. Elevation of media Na+ or Cl- in the presence of the other ion produced a saturable increase of JHCO3-. In the presence of Na+, Cl- stimulated JHCO3- when added to the mucosal but not the serosal medium. In the presence of Cl-, Na+ elevated JHCO3- when added to the serosal but not the mucosal medium. The ability of mucosal Cl- to stimulate JHCO3- was not apparently dependent on mucosal Na+. Simultaneous addition of 10 mM Cl- to the Na+ -free mucosal medium and 10 mM Na+ to the Cl- -free serosal medium stimulated JHCO3- above levels produced by serosal Na+ alone. In conclusion, intestinal HCO3- secretion required mucosal Cl- and serosal Na+ and did not involve mucosal NaCl cotransport. The results are consistent with a mucosal Cl- absorptive mechanism in series with parallel basolateral Na+ -H+ and Cl- -HCO3- exchange mechanisms.

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Chloride-bicarbonate exchange in the urinary bladder of the turtle. Independence from sodium ion

Cited by 10 publications

References 10 publications

Sulfate transport in rabbit ileum: Characterization of the serosal border anion exchange process

Sulfate transport in rabbit ileum: Characterization of the serosal border anion exchange process

A double-membrane model for urinary bicarbonate secretion

Intestinal HCO 3 − secretion inAmphiuma: Stimulation by mucosal Cl− and serosal Na+

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