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Transcellular relocation of tetrahydrobiopterin across Caco‐2 cells: A model study of tetrahydrobiopterin absorption through epithelial cells of intestinal mucosa
Author(s) -
Ohashi A.,
Fukumuro M.,
Sawabe K.,
Mamada K.,
Sugawara Y.,
Matsuoka H.,
Hasegawa H.
Publication year - 2009
Publication title -
journal of inherited metabolic disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 102
eISSN - 1573-2665
pISSN - 0141-8955
DOI - 10.1007/s10545-008-0961-3
Subject(s) - tetrahydrobiopterin , transcellular , intestinal mucosa , caco 2 , absorption (acoustics) , paracellular transport , intestinal epithelium , chemistry , epithelium , medicine , endocrinology , biology , in vitro , biochemistry , pathology , nitric oxide , nitric oxide synthase , physics , membrane , permeability (electromagnetism) , acoustics
Summary Oral administration of tetrahydrobiopterin (BH 4 ) has been known to be effective in treating BH 4 ‐deficient patients. It has long been established that BH 4 is absorbed by the intestinal mucosa. However, the mechanism for translocation of BH 4 across epithelial cells has not been elucidated. In order to study BH 4 transport mechanisms, Caco‐2 cells were employed in this study as an epithelial cell model. Caco‐2 cells were cultured (2 × 10 4 cells/0.3 cm 2 well) for 21 days in a 24‐well format using Transwell, a porous membrane‐based culture dish, at which point they had established themselves as a tight sheet with a definite polarity. When BH 4 (100 μmol/L) was given to cells from the apical side, a considerable translocation toward their basolateral side was noted. The rate of BH 4 movement was around 150 pmol/h per well. This was comparable to the highest rate of BH 4 uptake or its release so far obtained using a monolayer culture of Caco‐2 cells on an ordinary plastic plate. The transcellular movement of BH 4 across the polar culture on the porous membrane was effectively prevented by benzbromarone (10 μmol/L), a well known inhibitor of a group of transporters including urate transporter (URAT1), organic anion transporters (OATs), and multidrug‐resistance‐associated proteins (MRPs). It was thus concluded that in Caco‐2 cells, BH 4 moved across the cell interior in a rapid ligand‐specific manner that was driven by a transporter.