Mercury uptake by LLC-PK1 cells: dependence on temperature and membrane potential.
The purpose of this study was to investigate the mechanism of inorganic mercury (Hg) uptake in LLC-PK1 cells, a renal tubular epithelial cell line, and to compare the results with those reported previously by us in rat renal cortical epithelial (RCE) cells in primary culture. The LLC-PK1 cells were cultured for 3-12 days, incubated with 1 microM HgCl2 in Hanks' balanced salt solution at 4 or 37 degrees C for 30 min, and washed with phosphate-buffered saline containing BAL to remove the cell membrane-bound Hg. The uptake of Hg was higher in nonconfluent cultures than in confluent cultures and higher at 37 than at 4 degrees C. In confluent culture (Day 8) Hg uptake at 4 degrees C was only 27% of that at 37 degrees C. The initial accumulation of Hg (5 min) from different concentrations of HgCl2 (0.5-50 microM) was linear and did not show a tendency toward saturation, suggesting that a carrier-mediated process was not involved. Pretreatment of cells with 10 microM FCCP, a metabolic inhibitor and a proton ionophore, 0.5 mm DIDS, an anion transport inhibitor, or 0.5 mM ouabain, a Na+/K+-ATPase inhibitor, resulted in 72, 60, and 57% reduction in Hg uptake, respectively. Furthermore, replacement of 137 mm NaCl in the incubation medium with 137 mM KCl or LiCl or 274 mM mannitol caused 30, 45, and 87% reduction in Hg uptake, respectively. These results suggest that in LLC-PK1 cells, as in RCE cells, Hg uptake is inversely related to cell density and is influenced by membrane fluidity, membrane potential, and HCO3-/Cl- transporter.
Endo
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Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido 1757, Hokkaido, Ishikari-Tobetsu, 061-02, Japan.
Kimura
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Sakata
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Shaikh
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D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002452:Cell Count; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000502:physiology; D018374:LLC-PK1 Cells; D008094:Lithium / Q000494:pharmacology; D008560:Membrane Fluidity / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D008627:Mercuric Chloride / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013552:Swine; D013696:Temperature
D004791:Enzyme Inhibitors; D007476:Ionophores; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008627:Mercuric Chloride; D010042:Ouabain; D008094:Lithium; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium