title: Effects of fifteen rare-earth metals on Ca2+ influx in tobacco cells.
abstract: Effects of naturally existing rare-earth metals (REMs; atomic numbers, 39, 57-60, 62-71; Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), added as chloride salts, on Ca2+ influx induced by two different stimuli, namely hypoosmotic shock and hydrogen peroxide, were examined in a suspension-cultured transgenic cell line of BY-2 tobacco cells expressing aequorin, a Ca(2+)-sensitive luminescent protein in cytosol. Most REM salts used here showed inhibitory effect against Ca2+ influx. Especially NdCl3, SmCl3, EuCl3, GdCl3 and TbCl3 showed the most robust inhibitory action. In contrast, LuCl3, YbCl3, ErCl3 and YCl3 were shown to be poor inhibitors of Ca2+ influx. Since REMs tested here form a sequential range of ionic radii from 86.1 to 103.2 pm and the optimal range of ionic radii required for blocking the flux of Ca2+ was determined for each stimulus. The hydrogen peroxide-induced Ca2+ influx was optimally blocked by REMs with a broad range of ionic radii (93.8-101 pm) which is slightly smaller than or similar to that of Ca2+ (100 pm), while the hypoosmotically induced flux of Ca2+ was inhibited optimally by few REMs with a narrower range of relatively smaller ionic radii around that of Gd3+ (93.8 pm) a well known inhibitor of stretch-activated channels. Possible applications of such series of channel blockers in elucidation of plant signal transduction pathways are encouraged.
authors.affiliation: Graduate School of Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0135, Japan.
authors.forename: Cun
authors.initials: C
authors.lastname: Lin
authors.forename: Takashi
authors.initials: T
authors.lastname: Kadono
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Yoshizuka
authors.forename: Takuya
authors.initials: T
authors.lastname: Furuichi
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kawano
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D008674:Metals, Rare Earth / Q000494:pharmacology*; D014026:Nicotiana / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002712:Chlorides; D008674:Metals, Rare Earth; D006861:Hydrogen Peroxide; D002118:Calcium