Chronic and selective inhibition of basolateral membrane Na-K-ATPase uniquely regulates brush border membrane Na absorption in intestinal epithelial cells.
Am J Physiol Cell Physiol
; 308(8): C650-6, 2015 Apr 15.
Article
en En
| MEDLINE
| ID: mdl-25652450
ABSTRACT
Na-K-ATPase, an integral membrane protein in mammalian cells, is responsible for maintaining the favorable intracellular Na gradient necessary to promote Na-coupled solute cotransport processes [e.g., Na-glucose cotransport (SGLT1)]. Inhibition of brush border membrane (BBM) SGLT1 is, at least in part, due to the diminished Na-K-ATPase in villus cells from chronically inflamed rabbit intestine. The aim of the present study was to determine the effect of Na-K-ATPase inhibition on the two major BBM Na absorptive pathways, specifically Na-glucose cotransport and Na/H exchange (NHE), in intestinal epithelial (IEC-18) cells. Na-K-ATPase was inhibited using 1 mM ouabain or siRNA for Na-K-ATPase-α1 in IEC-18 cells. SGLT1 activity was determined as 3-O-methyl-D-[(3)H]glucose uptake. Na-K-ATPase activity was measured as the amount of inorganic phosphate released. Treatment with ouabain resulted in SGLT1 inhibition at 1 h but stimulation at 24 h. To further characterize this unexpected stimulation of SGLT1, siRNA silencing was utilized to inhibit Na-K-ATPase-α1. SGLT1 activity was significantly upregulated by Na-K-ATPase silencing, while NHE3 activity remained unaltered. Kinetics showed that the mechanism of stimulation of SGLT1 activity was secondary to an increase in affinity of the cotransporter for glucose without a change in the number of cotransporters. Molecular studies demonstrated that the mechanism of stimulation was not secondary to altered BBM SGLT1 protein levels. Chronic and direct silencing of basolateral Na-K-ATPase uniquely regulates BBM Na absorptive pathways in intestinal epithelial cells. Specifically, while BBM NHE3 is unaffected, SGLT1 is stimulated secondary to enhanced affinity of the cotransporter.
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Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Intercambiadores de Sodio-Hidrógeno
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ATPasa Intercambiadora de Sodio-Potasio
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Transportador 1 de Sodio-Glucosa
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Absorción Intestinal
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Microvellosidades
Límite:
Animals
Idioma:
En
Revista:
Am J Physiol Cell Physiol
Asunto de la revista:
FISIOLOGIA
Año:
2015
Tipo del documento:
Article