Na+-Coupled Nutrient Cotransport Induced Luminal Negative Potential and Claudin-15 Play an Important Role in Paracellular Na+ Recycling in Mouse Small Intestine.
Int J Mol Sci
; 21(2)2020 Jan 07.
Article
en En
| MEDLINE
| ID: mdl-31936130
ABSTRACT
Many nutrients are absorbed via Na+ cotransport systems, and therefore it is predicted that nutrient absorption mechanisms require a large amount of luminal Na+. It is thought that Na+ diffuses back into the lumen via paracellular pathways to support Na+ cotransport absorption. However, direct experimental evidence in support of this mechanism has not been shown. To elucidate this, we took advantage of claudin-15 deficient (cldn15-/-) mice, which have been shown to have decreased paracellular Na+ permeability. We measured glucose-induced currents (ΔIsc) under open- and short-circuit conditions and simultaneously measured changes in unidirectional 22Na+ fluxes (ΔJNa) in Ussing chambers. Under short-circuit conditions, application of glucose resulted in an increase in ΔIsc and unidirectional mucosal to serosal 22Na+ (∆JNaMS) flux in both wild-type and cldn15-/- mice. However, under open-circuit conditions, ΔIsc was observed but ∆JNaMS was strongly inhibited in wild-type but not in cldn15-/- mice. In addition, in the duodenum of mice treated with cholera toxin, paracellular Na+ conductance was decreased and glucose-induced ∆JNaMS increment was observed under open-circuit conditions. We concluded that the Na+ which is absorbed by Na+-dependent glucose cotransport is recycled back into the lumen via paracellular Na+ conductance through claudin-15, which is driven by Na+ cotransport induced luminal negativity.
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Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Sodio
/
Nutrientes
/
Claudinas
/
Intestino Delgado
Límite:
Animals
Idioma:
En
Año:
2020
Tipo del documento:
Article