ISSN:
1432-1424
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Bicarbonate is transferred across the serosal (S) membrane of the epithelial cells of the turtle bladder in two directions. Cellular HCO 3 − generated behind the H+ pump moves across this membrane into the serosal solution. This efflux of HCO 3 − is inhibited by SITS (4-isothiocyano-4′-acetamido-2,2′-disulfonic stilbene). When HCO 3 − is added to the serosal solution it is transported across the epithelium in exchange for absorbed Cl−. This secretory HCO 3 − flow traverses the serosal cell membrane in the opposite direction. In this study the effects of serosal addition of 5×10−4 m SITS on HCO 3 − secretion and Cl− absorption were examined. The rate of H+ secretion was brought to zero by an opposing pH gradient, and 20mm HCO 3 − was added toS. HCO 3 − secretion, measured by pH stat titration, was equivalent to the increase inM→S Cl− flux after HCO 3 − addition. Neither theS→M flux of HCO 3 − nor theM→S flux of Cl− were affected by SITS. In the absence of electrochemical gradients, net Cl− absorption was observed only in the presence of HCO 3 − in the media; under such conditions, unidirectional and net fluxes of Cl− were not altered by serosal or mucosal SITS. H+ secretion, however, measured simultaneously as the short-circuit current in ouabain-treated bladders decreased markedly after serosal SITS. The inhibition of the efflux of HCO 3 − in series with the H+ pump and the failure of SITS to affect HCO 3 − secretion and Cl− absorption suggest that the epithelium contains at least two types of transport systems for bicarbonate in the serosal membrane.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869045
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