Methylmercury elicits intracellular Zn2+ release in rat thymocytes: its relation to methylmercury-induced decrease in cellular thiol content.
We have previously revealed that thimerosal, an organomercurial preservative, increases intracellular Zn(2+) concentration in rat thymocytes. Because thimerosal contains ethylmercury that confers the toxicity, it is a possibility that methylmercury (MetHg), an environmental pollutant, also increases intracellular Zn(2+) concentration. This possibility was tested by measuring intracellular Zn(2+) level with FluoZin-3, a fluorescent probe for intracellular Zn(2+). MetHg at concentrations ranging from 100 nM to 1 microM significantly increased the intensity of FluoZin-3 fluorescence, an indicator for intracellular Zn(2+) concentration, under external Ca(2+)- and Zn(2+)-free condition in a concentration-dependent manner. TPEN, a chelator for intracellular Zn(2+), completely diminished the MetHg-induced augmentation of FluoZin-3 fluorescence. MetHg at 100 nM or more significantly decreased the intensity of 5-chlormethylfluorescein fluorescence, an indicator for cellular thiol content. Such MetHg-induced changes in the fluorescence were correlated with a coefficient of -0.917. Taken together, it is suggested that submicromolar MetHg releases Zn(2+) from intracellular thiol, resulting in the increase in intracellular Zn(2+) concentration. However, it is unlikely that MetHg at critical maternal blood concentration (27 nM) affects intracellular Zn(2+) homeostasis.
Kawanai
Takuya
T
Laboratory of Cellular Signaling, Faculty of Integrated Arts and Sciences, The University of Tokushima, Minami-Jyosanijuma 1-1, Tokushima 770-8502, Japan.
Satoh
Masaya
M
Murao
Koji
K
Oyama
Yasuo
Y
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008767:Methylmercury Compounds / Q000633:toxicity*; D011083:Polycyclic Compounds; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
D002614:Chelating Agents; D005029:Ethylenediamines; C451182:FluoZin-3; D005452:Fluoresceins; D005456:Fluorescent Dyes; D008767:Methylmercury Compounds; D011083:Polycyclic Compounds; D013438:Sulfhydryl Compounds; C069306:5-chloromethylfluorescein; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine