Base secretion in rat distal colon: ionic requirements.
Am J Physiol
; 258(6 Pt 1): G825-32, 1990 Jun.
Article
em En
| MEDLINE
| ID: mdl-2163204
ABSTRACT
To evaluate the ionic requirements of colonic base secretion, segments of rat distal colon were studied under short-circuited conditions. Net base flux was composed of an active secretory component and a diffusive component. Studied in the absence of a transepithelial HCO3- concentration gradient, active base secretion was dependent on the HCO3- concentration of the bathing solution but was not influenced by the CO2 tension or pH. Base secretion appeared to saturate with a Km of 33 +/- 9 mM and was inhibited by ouabain. The diffusive component was characterized by an apparent permeability coefficient to HCO3- of 8.9 +/- 0.9 x 10(-6) cm/s. In addition to requiring HCO3- on the serosal surface, net base secretion was inhibited by reducing the Na+ concentration in the serosal medium and the Cl- concentration in the mucosal medium. These data suggest that colonic base secretion involves HCO3- entry across the basolateral surface, energized by the Na+ gradient, and HCO3- exit across the apical surface in exchange for Cl-.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Bicarbonatos
/
Colo
/
Mucosa Intestinal
Limite:
Animals
Idioma:
En
Ano de publicação:
1990
Tipo de documento:
Article