Hg2+ signaling in trout hepatoma (RTH-149) cells: involvement of Ca2+-induced Ca2+ release.
Mercury is a non-essential heavy metal affecting intracellular Ca2+ dynamics. We studied the effects of Hg2+ on [Ca2+]i in trout hepatoma cells (RTH-149). Confocal imaging of fluo-3-loaded cells showed that Hg2+ induced dose-dependent, sustained [Ca2+]i transient, triggered intracellular Ca2+ waves, stimulated Ca2+-ATPase activity, and promoted InsP3 production. The effect of Hg2+ was reduced by the Ca2+ channel blocker verapamil and totally abolished by extracellular GSH, but was almost unaffected by cell loading with the heavy metal chelator TPEN or esterified GSH. In a Ca2+-free medium, Hg2+ induced a smaller [Ca2+]i transient, that was unaffected by TPEN, but was abolished by U73122, a PLC inhibitor, and by cell loading with GDP-betaS, a G protein inhibitor, or heparin, a blocker of intracellular Ca2+ release. Data indicate that Hg2+ induces Ca2+ entry through verapamil-sensitive channels, and intracellular Ca2+ release via a G protein-PLC-InsP3 mechanism. However, in cells loaded with heparin and exposed to Hg2+ in the presence of external Ca2+, the [Ca2+]i rise was maximally reduced, indicating that the global effect of Hg2+ is not a mere sum of Ca2+ entry plus Ca2+ release, but involves an amplification of Ca2+ release operated by Ca2+ entry through a CICR mechanism.
Burlando
Bruno
B
Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale Amedeo Avogadro, Corso Borsalino 54, 15100 Alessandria, Italy. burlando@unipmn.it
Bonomo
Marco
M
Fabbri
Elena
E
Dondero
Francesco
F
Viarengo
Aldo
A
D000814:Aniline Compounds / Q000032:analysis / Q000493:pharmacokinetics; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D045744:Cell Line, Tumor / Q000187:drug effects; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D004963:Estrenes / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D006651:Histocytochemistry; D015544:Inositol 1,4,5-Trisphosphate / Q000032:analysis / Q000378:metabolism; D007700:Kinetics; D008628:Mercury / Q000494:pharmacology / Q000633:toxicity*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010740:Phospholipases / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014337:Trout; D014700:Verapamil / Q000494:pharmacology; D014966:Xanthenes / Q000032:analysis / Q000493:pharmacokinetics
D000814:Aniline Compounds; D004963:Estrenes; D005029:Ethylenediamines; D011760:Pyrrolidinones; D013873:Thionucleotides; D014966:Xanthenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D006153:Guanosine Diphosphate; C059715:Fluo-3; C023427:guanosine 5'-O-(2-thiodiphosphate); C042431:S-ethyl glutathione; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D014700:Verapamil; D010740:Phospholipases; D017301:Ca(2+) Mg(2+)-ATPase; D019204:GTP-Binding Proteins; D008628:Mercury; D005978:Glutathione; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; D002118:Calcium