title: Na(+)- and energy-dependent transport of cadmium into LLC-PK1 cells.
abstract: Effects of sodium ions (Na+) and metabolic inhibitors on cadmium (Cd) uptake were investigated in LLC-PK1 cells derived from pig kidney under the nontoxic conditions of Cd. The inoculated cells became confluent on day 7 after the logarithmic growth phase. The initial uptake of Cd (1-60 microM) by the confluent cells (day 7) was assayed. The relationship between the Cd uptake at 37 degrees C and Cd concentration was nonlinear, but the relationship at 4 degrees C was linear. Subtraction of the Cd uptake at 4 degrees C from that at 37 degrees C showed a saturable uptake against the Cd concentration. By the Eadie-Hofstee analysis of saturable uptake, Km and Vmax were 24.6 microM and 164 pmol Cd/mg protein/min, respectively. The uptake of Cd by the cells was significantly decreased by ouabain and the metabolic inhibitors, and by the replacement of Na+ with potassium or choline ion in the incubation medium. These results suggest that Cd is incorporated into the confluent LLC-PK1 cells not only by simple diffusion but also by the carrier-mediated transport involved in Na(+)- and energy-dependent process(es).
authors.affiliation: Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Endo
authors.forename: O
authors.initials: O
authors.lastname: Kimura
authors.forename: M
authors.initials: M
authors.lastname: Sasaya
authors.forename: M
authors.initials: M
authors.lastname: Takada
authors.forename: M
authors.initials: M
authors.lastname: Sakata
mesh_terms: D019297:2,4-Dinitrophenol; D000818:Animals; D001693:Biological Transport, Active; D002104:Cadmium / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002455:Cell Division; D004140:Dinitrophenols / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018374:LLC-PK1 Cells / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D013552:Swine; D013696:Temperature; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D004140:Dinitrophenols; D004791:Enzyme Inhibitors; D014475:Uncoupling Agents; D002104:Cadmium; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D010042:Ouabain; D012964:Sodium; D011190:Potassium Cyanide; D019297:2,4-Dinitrophenol; D002118:Calcium