title: Role of Na+, K+-ATPase alpha1 subunit in the intracellular accumulation of cisplatin.
abstract: The present study was undertaken to identify what regulates intracellular cisplatin (CDDP) accumulation and what changes in membrane fraction of CDDDP-resistant cell line. The CDDP-resistant rat hepatoma cell line, H4-II-E/CDDP, shows a significant decrease in intracellular platinum accumulation compared with parental H4-II-E cells, although there was no difference in the efflux of CDDP between these two cell lines. In this study, we examined the contribution of functional change in active transport to the CDDP resistance of H4-II-E/CDDP cells. Compared with the resistant cells, platinum accumulation in the parental cells was clearly decreased by low temperature or ATP depletion. In addition, the Na+, K+-ATPase inhibitor ouabain and the K+ channel inhibitor tetraethylammonium decreased platinum accumulation in parental cells but did not change the accumulation in resistant cells. Amphotericin B, an antifungal agent, increased the intracellular platinum accumulation in resistant cells to the same level as in parent cells. Western blot analysis demonstrated that the Na+, K+-ATPase alpha1 subunit was reduced in resistant cells compared with the parental cells, although there was no difference in the expression of the beta1 subunit between the two cell lines. Furthermore, the Na+, K+-ATPase alpha1 subunit of H4-II-E was decreased following a 24-h exposure to CDDP. These results suggest that Na+, K+-ATPase-dependent active transport of CDDP does not occur in resistant cells, and, furthermore, our findings provide the first evidence that the Na+, K+-ATPase alpha1 subunit plays an important role in the transport of CDDP.
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Nishi-ku, Kobe, 651-2180 Japan. skisimot@pharm.kobegakuin.ac.jp
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kishimoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kawazoe
authors.forename: Mako
authors.initials: M
authors.lastname: Ikeno
authors.forename: Mizuha
authors.initials: M
authors.lastname: Saitoh
authors.forename: Yukari
authors.initials: Y
authors.lastname: Nakano
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nishi
authors.forename: Shoji
authors.initials: S
authors.lastname: Fukushima
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Takeuchi
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics*; D001693:Biological Transport, Active; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000493:pharmacokinetics*; D019327:Copper Sulfate / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C499075:Atp1a1 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase; D019327:Copper Sulfate; D002945:Cisplatin