Nucleotide Sequence of the Na+/H+ Exchanger-8 in Patients With Congenital Sodium Diarrhea

Department of Pediatrics, Mattel Children's Hospital, David Geffen School of Medicine at the University of California, Los Angeles, USA.
Journal of pediatric gastroenterology and nutrition (Impact Factor: 2.63). 06/2011; 53(5):474-7. DOI: 10.1097/MPG.0b013e318227ad6e
Source: PubMed


Sodium absorption by the intestine is mediated by brush border Na/H exchangers, which include the NHE3 and NHE8 isoforms. We demonstrated a maturational decrease in NHE8 and increase in NHE3 in mouse intestine mRNA abundance and brush border membrane protein abundance, indicating a developmental switch of isoforms. Congenital sodium diarrhea is a rare autosomal recessive disorder characterized by polyhydramnios, hyponatremia, metabolic acidosis, and diarrhea with a high sodium content. Previous studies using intestinal brush border membrane vesicles from patients with this disorder have demonstrated a decrease in Na/H exchanger activity. Because some patients with congenital sodium diarrhea improve with age and knowing the developmental switch from NHE8 to NHE3, NHE8 may be a candidate gene for this disorder. We sequenced NHE8 from 5 patients with this disorder and found no disease-causing homozygous mutations. Although brush border membrane Na/H exchange activity may be decreased, exonic mutations in NHE8 cannot account for this disorder in these subjects.

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