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Article

Na+-Coupled Nutrient Cotransport Induced Luminal Negative Potential and Claudin-15 Play an Important Role in Paracellular Na+ Recycling in Mouse Small Intestine

1
Laboratory of Physiology, School of Food and Nutritional Sciences, University of Shizuoka, Yada 52-1, Suruga-ku, Shizuoka 422-8526, Japan
2
Laboratory of Biochemistry, Department of Biopharmaceutical Sciences, Gifu Pharmaceutical University, Gifu 501-1196, Japan
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Int. J. Mol. Sci. 2020, 21(2), 376; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21020376
Received: 6 December 2019 / Revised: 27 December 2019 / Accepted: 30 December 2019 / Published: 7 January 2020
(This article belongs to the Special Issue Sodium Intake and Related Diseases)
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. View Full-Text
Keywords: tight junction; Na+ cotransport; leaky epithelia tight junction; Na+ cotransport; leaky epithelia
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MDPI and ACS Style

Nakayama, M.; Ishizuka, N.; Hempstock, W.; Ikari, A.; Hayashi, H. 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. 2020, 21, 376. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21020376

AMA Style

Nakayama M, Ishizuka N, Hempstock W, Ikari A, Hayashi H. Na+-Coupled Nutrient Cotransport Induced Luminal Negative Potential and Claudin-15 Play an Important Role in Paracellular Na+ Recycling in Mouse Small Intestine. International Journal of Molecular Sciences. 2020; 21(2):376. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21020376

Chicago/Turabian Style

Nakayama, Michiko, Noriko Ishizuka, Wendy Hempstock, Akira Ikari, and Hisayoshi Hayashi. 2020. "Na+-Coupled Nutrient Cotransport Induced Luminal Negative Potential and Claudin-15 Play an Important Role in Paracellular Na+ Recycling in Mouse Small Intestine" International Journal of Molecular Sciences 21, no. 2: 376. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21020376

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