Health from a healthy gut

Healthy living requires an understanding of intestinal function

All segments of the intestine from the duodenum to the distal colon have mechanisms for both absorbing and secreting water and electrolytes, thereby supporting nutrient digestion and absorption. These mechanisms are mediated by a variety of channels and transporters in the epithelial membrane as well as the paracellular pathway. Many neurohumoral factors are known to control these processes. Disorders of absorption and secretion cause pathological conditions such as malabsorption (malnutrition) and diarrhea (dehydration). Our research focuses are: (1) molecular mechanisms and regulation of intestinal NaCl absorption, and (2) permeability role of the tight junction.

1. Molecular mechanisms and regulation of intestinal NaCl absorption
A Cl/HCO3 exchanger, DRA (slc26a3) is one of the main apical Cl transporters responsible for transepithelial Cl absorption. We investigate its function using both heterologous expression system and a DRA-deficient mouse model.
2. Permeability role of tight junction
The tight junction barrier is not absolute but is selectively permeable. We investigate the role of intestinal tight junction permeability in maintaining luminal electrolyte homeostasis and nutrient absorption.

Assisstant Professor

Hisayoshi HayashiPhD


Noriko IshizukaPhD

Details are here



Intestinal NaCl absorption is mediated by Na-nutrient-coupled absorption (1) and NaCl-coupled absorption (2), while secretion by electrogenic Cl secretion (3). In NaCl-coupled absorption, a Cl/HCO3 exchanger is assumed to be responsible for apical Cl uptake.


One of the tight junctional proteins, claudin-15, renders intestinal tight junction cation permeable, thereby providing Na to maintain luminal Na homeostasis. In a claudin-15 deficient mouse, Na-coupled nutrient absorption is hampered by a decrease in luminal Na concentration.


  1. Am J Physiol., 302, C781–95 (2012)
  2. Gastroenterology, 140, 913–23 (2011)
  3. Am J Physiol., 299, G115–125 (2010)
  4. J Cell Biol., 188, 547–563 (2010)
  5. Am J Physiol., 299, C1279–90 (2009)
  6. Am J Physiol., 294, C526–34 (2008)
  7. Gastroenterology, 134, 523–534 (2008)
  8. Biomed Res., 28, 239246 (2007)
  9. Pflugers Arch., 454, 253–262 (2007)
  10. J Cell Biol., 169, 21–8 (2005)
  11. J Gen Physiol.,123, 491-504 (2004)
  12. Am J Physiol., 284, G617–28 (2003)
  13. J Biol Chem., 277, 11090–96 (2002)