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Amino Acids. 2017 Apr;49(4):725-734. doi: 10.1007/s00726-016-2374-1. Epub 2016 Dec 15.

Na+/H+ exchanger 3 inhibitor diminishes the amino-acid-enhanced transepithelial calcium transport across the rat duodenum.

Author information

1
Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand.
2
Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
3
Faculty of Allied Health Sciences, Burapha University, Chonburi, 20131, Thailand.
4
Department of Biochemistry, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand.
5
Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand. naratt@narattsys.com.
6
Center of Calcium and Bone Research (COCAB), Faculty of Science, Mahidol University, Bangkok, 10400, Thailand. naratt@narattsys.com.
7
Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, 73170, Thailand. naratt@narattsys.com.

Abstract

Na+/H+ exchanger (NHE)-3 is important for intestinal absorption of nutrients and minerals, including calcium. The previous investigations have shown that the intestinal calcium absorption is also dependent on luminal nutrients, but whether aliphatic amino acids and glucose, which are abundant in the luminal fluid during a meal, similarly enhance calcium transport remains elusive. Herein, we used the in vitro Ussing chamber technique to determine epithelial electrical parameters, i.e., potential difference (PD), short-circuit current (Isc), and transepithelial resistance, as well as 45Ca flux in the rat duodenum directly exposed on the mucosal side to glucose or various amino acids. We found that mucosal glucose exposure led to the enhanced calcium transport, PD, and Isc, all of which were insensitive to NHE3 inhibitor (100 nM tenapanor). In the absence of mucosal glucose, several amino acids (12 mM in the mucosal side), i.e., alanine, isoleucine, leucine, proline, and hydroxyproline, markedly increased the duodenal calcium transport. An inhibitor for NHE3 exposure on the mucosal side completely abolished proline- and leucine-enhanced calcium transport, but not transepithelial transport of both amino acids themselves. In conclusion, glucose and certain amino acids in the mucosal side were potent stimulators of the duodenal calcium absorption, but only amino-acid-enhanced calcium transport was NHE3-dependent.

KEYWORDS:

Aliphatic amino acid; Calcium transport; Duodenum; Tenapanor; Ussing chamber

PMID:
27981415
DOI:
10.1007/s00726-016-2374-1
[Indexed for MEDLINE]

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