title: Increase in intracellular Zn2+ concentration by thimerosal in rat thymocytes: intracellular Zn2+ release induced by oxidative stress.
abstract: Thimerosal (TMR), an ethylmercury-containing preservative in pharmaceutical products, was recently reported to increase intracellular Zn(2+) concentration. Therefore, some health concerns about the toxicity of TMR remain because of physiological and pathological roles of Zn(2+). To reveal the property of TMR-induced increase in intracellular Zn(2+) concentration, the effect of TMR on FluoZin-3 fluorescence, an indicator of intracellular Zn(2+), of rat thymocytes was examined. TMR at concentrations ranging from 0.3 microM to 10 microM increased the intensity of FluoZin-3 fluorescence in a concentration-dependent manner under external Ca(2+)- and Zn(2+)-free condition. The threshold concentration was 0.3-1 microM. The increase in the intensity was significant when TMR concentration was 1 microM or more. N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a chelator for intracellular Zn(2+), completely attenuated the TMR-induced augmentation of FluoZin-3 fluorescence. Hydrogen peroxide (H(2)O(2)) and N-ethylmaleimide, reducing cellular thiol content, significantly increased FluoZin-3 fluorescence intensity and decreased 5-chloromethylfluorescein (5-CMF) fluorescence intensity, an indicator for cellular thiol. The correlation coefficient between TMR-induced augmentation of FluoZin-3 fluorescence and attenuation of 5-CMF fluorescence was -0.882. TMR also attenuated the 5-CMF fluorescence in the presence of TPEN. Simultaneous application of H(2)O(2) and TMR synergistically augmented the FluoZin-3 fluorescence. It is suggested that TMR increases intracellular Zn(2+) concentration via decreasing cellular thiol content.
authors.affiliation: Laboratory of Cellular Signaling, Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770-8502, Japan.
authors.forename: Erika
authors.initials: E
authors.lastname: Hashimoto
authors.forename: Toshihisa B
authors.initials: TB
authors.lastname: Oyama
authors.forename: Keisuke
authors.initials: K
authors.lastname: Oyama
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Tomohiro M
authors.initials: TM
authors.lastname: Oyama
authors.forename: Toshiko
authors.initials: T
authors.lastname: Ueha-Ishibashi
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Okano
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Oyama
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D006861:Hydrogen Peroxide / Q000633:toxicity; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects*; D011083:Polycyclic Compounds; D011310:Preservatives, Pharmaceutical / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013849:Thimerosal / Q000008:administration & dosage / Q000633:toxicity*; D013950:Thymus Gland / Q000166:cytology; D015032:Zinc / Q000378:metabolism*
chemical_list: C451182:FluoZin-3; D005456:Fluorescent Dyes; D011083:Polycyclic Compounds; D011310:Preservatives, Pharmaceutical; D013438:Sulfhydryl Compounds; D013849:Thimerosal; D006861:Hydrogen Peroxide; D015032:Zinc