Open AccessFurther Analysis of Cadmium Uptake from Apical Membrane of LLC‐PK 1 Cells via Inorganic Anion Exchanger
Author(s) -
Endo Tetsuya,
Kimura Osamu,
Sakata Masakatsu
Publication year - 1999
Publication title -
pharmacology & toxicology
Language(s) - English
Resource type - Journals
eISSN - 1600-0773
pISSN - 0901-9928
DOI - 10.1111/j.1600-0773.1999.tb00898.x
Subject(s) - dids , chemistry , egta , membrane , chelation , apical membrane , cadmium , biophysics , incubation , biochemistry , membrane transport , ion exchange , calcium , inorganic chemistry , ion , biology , organic chemistry
This study was undertaken to analyze Cd uptake via the inorganic anion exchanger (HCO 3 − /Cl − ) by LLC‐PK 1 cells cultured on permeable membranes. LLC‐PK 1 cells were incubated at 37° with 1 μM CdCl 2 added to the apical medium, and Cd accumulation in the cells was fractionated into a membrane‐bound (non‐internalized) Cd fraction and an internalized Cd fraction using ethyleneglycol‐bis‐(p‐aminoethylether)‐N, N, N', N'‐tetraacetic acid (EGTA), a chelating agent for Cd. Incubation at a lower temperature (4°) significantly decreased the membrane‐bound Cd fraction, and drastically decreased the internalized Cd fraction. Addition of NaHCO 3 3 (a stimulator of Cd uptake via inorganic anion exchanger) to the apical medium significantly increased both membrane‐bound and internalized Cd fractions, and this increase was greater for the internalized fraction. Pretreatment of cells with 4, 4′‐diisothiocyanostilbene‐2, 2′‐disulfonic acid (DIDS), a specific inhibitor of inorganic anion exchangers, significantly decreased the internalized Cd fraction without changing the membrane‐bound Cd fraction. Addition of NaHCO 3 did not effect both Cd fractions in DIDS‐pretreated cells. These results suggest that most of Cd binds non‐specifically to the apical membrane surface and then is internalized via simple diffusion and some Cd specifically binds to the inorganic anion exchanger and is internalized in a metabolism‐dependent manner.