title: Some characteristics of membrane Cd²+ transport in rat thymocytes: an analysis using Fluo-3.
abstract: Although cadmium-induced apoptosis of lymphocytes is one of common features in the immunotoxicity of cadmium, the membrane pathway for intracellular cadmium accumulation is not fully elucidated. To characterize membrane Cd(2+) transport of rat thymocytes, the change in intracellular Cd(2+) concentration under various conditions was examined by the use of Fluo-3, a fluorescent probe for monitoring the change in intracellular concentration of divalent metal cations. The membrane Cd(2+) transport was estimated by the augmentation of Fluo-3 fluorescence induced by bath application of CdCl(2). Lowering temperature strongly suppressed the augmentation of Fluo-3 fluorescence by CdCl(2), suggesting that the metabolic process can be involved in membrane Cd(2+) transport. External acidification (decreasing pH) and membrane depolarization by adding KCl attenuated the augmentation, indicating the requirement of electrochemical driving force for membrane Cd(2+) transport into the cells. Bath application of CaCl(2) and ZnCl(2) equally decreased the augmentation, suggesting their competition with Cd(2+) at the membrane transport. The augmentation by CdCl(2) was lesser in the cells treated with N-ethylmaleimide inducing chemical depletion of cellular thiols. The result suggests the contribution of sulfhydryl groups to membrane Cd(2+) transport. Taken together, it is suggested that the cells possess a temperature-sensitive membrane Cd(2+) pathway, driven by electrochemical gradient of Cd(2+) and transmembrane potential, with competitive binding site. Based on the characteristics described above, it is unlikely that the membrane Cd(2+) transport in rat thymocytes is attributed to a single transport system although it has characteristics that are similar to those of divalent cation transporter 1.
authors: Laboratories of Cellular Signaling, Environmental Biology, and Organometallic Chemistry, Faculty of Integrated Arts and Sciences, The University of Tokushima, 1-1 Minami-Jyosanjima, Tokushima 770-8502, Japan.
authors: Takuya
authors: T
authors: Kawanai
authors: Masahiro
authors: M
authors: Fujinaga
authors: Kazuki
authors: K
authors: Koizumi
authors: Isao
authors: I
authors: Kurotani
authors: Erika
authors: E
authors: Hashimoto
authors: Masaya
authors: M
authors: Satoh
authors: Shoji
authors: S
authors: Imai
authors: Norikazu
authors: N
authors: Miyoshi
authors: Yasuo
authors: Y
authors: Oyama
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D000818:Animals; D001692:Biological Transport; D002104:Cadmium / Q000032:analysis / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D005434:Flow Cytometry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence; D060168:Thymocytes / Q000737:chemistry / Q000378:metabolism*; D014966:Xanthenes / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D005456:Fluorescent Dyes; D014966:Xanthenes; D002104:Cadmium; C059715:Fluo-3