Dietary Na+ depletion up-regulates NKCC1 expression and enhances electrogenic Cl- secretion in rat proximal colon.
Cell Mol Life Sci
; 80(8): 209, 2023 Jul 17.
Article
em En
| MEDLINE
| ID: mdl-37458846
ABSTRACT
The corticosteroid hormone, aldosterone, markedly enhances K+ secretion throughout the colon, a mechanism critical to its role in maintaining overall K+ balance. Previous studies demonstrated that basolateral NKCC1 was up-regulated by aldosterone in the distal colon specifically to support K+ secretion-which is distinct from the more well-established role of NKCC1 in supporting luminal Cl- secretion. However, considerable segmental variability exists between proximal and distal colonic ion transport processes, especially concerning their regulation by aldosterone. Furthermore, delineating such region-specific effects has important implications for the management of various gastrointestinal pathologies. Experiments were therefore designed to determine whether aldosterone similarly up-regulates NKCC1 in the proximal colon to support K+ secretion. Using dietary Na+ depletion as a model of secondary hyperaldosteronism in rats, we found that proximal colon NKCC1 expression was indeed enhanced in Na+-depleted (i.e., hyperaldosteronemic) rats. Surprisingly, electrogenic K+ secretion was not detectable by short-circuit current (ISC) measurements in response to either basolateral bumetanide (NKCC1 inhibitor) or luminal Ba2+ (non-selective K+ channel blocker), despite enhanced K+ secretion in Na+-depleted rats, as measured by 86Rb+ fluxes. Expression of BK and IK channels was also found to be unaltered by dietary Na+ depletion. However, bumetanide-sensitive basal and agonist-stimulated Cl- secretion (ISC) were significantly enhanced by Na+ depletion, as was CFTR Cl- channel expression. These data suggest that NKCC1-dependent secretory pathways are differentially regulated by aldosterone in proximal and distal colon. Development of therapeutic strategies in treating pathologies related to aberrant colonic K+/Cl- transport-such as pseudo-obstruction or ulcerative colitis-may benefit from these findings.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Bumetanida
/
Aldosterona
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Cell Mol Life Sci
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2023
Tipo de documento:
Article
País de afiliação:
Estados Unidos