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AQP9 and UT‐A facilitate hepatocyte basolateral membrane urea permeability in mouse
Author(s) -
Jelen Sabina Katarzyna,
Gena Patrizia,
Lebeck Janne,
Prætorius Jeppe,
Fenton Robert,
Frøkiaer Jørgen,
Nielsen Søren,
Calamita Giuseppe,
Rützler Michael
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1110.1
Subject(s) - phloretin , urea , hepatocyte , chemistry , permeability (electromagnetism) , biochemistry , urea cycle , medicine , membrane , in vitro , amino acid , arginine
In mammals, nitrogen from protein degradation is disposed as urea. Several studies have investigated expression of urea transporters in hepatocytes, where urea is produced. Nevertheless, the role of protein facilitated urea transport in liver remains unknown. In the presented study we determine urea permeability in isolated basolateral hepatocyte membranes by stopped flow light scattering measurements. The urea channel inhibitors phloretin and dimethylurea reduced the urea permeability by 70% and 40%, respectively. In basolateral membranes isolated from AQP9 (AQP9−/−) and UT‐A (UT‐A−/−) single knockout, and AQP9−/−:UTA−/− double knockout mice, urea permeability (Purea) was decreased by 30%, 40%, and 76%, respectively, compared to wild type mice. In addition, we investigated the physiological role of AQP9 in mouse hepatocyte function following exposure to high oral glutamine doses or high protein diet. These conditions did not affect the concentrations of urea or ammonia in AQP9−/− mouse tissues and plasma, respectively. Similarly, hepatocyte urea synthesis of UT‐A−/− mice appeared normal. We currently conclude that both, AQP9 and a UT‐A gene product, constitute primary but redundant urea channels in hepatocytes. This study was supported by the Lundbeck Foundation.