title: Zinc ions cause the thimerosal-induced signal of fluorescent calcium probes in lymphocytes.
abstract: Most fluorescent probes for the investigation of calcium signaling also detect zinc ions. Consequently, changes in the intracellular zinc concentration could be mistaken for calcium signals. Thimerosal (TMS) is used as a calcium-mobilizing agent and we analyzed the contribution of zinc ions to the signal observed with fluorescent calcium probes after TMS stimulation. Our findings show that the fluorescent signal in lymphocytes is entirely due to zinc release. Experiments in the T lymphocyte cell line Jurkat and primary human lymphocytes show that TMS and its active metabolite, ethyl mercury, cause an increase in signal intensity with probes designed for the detection of either calcium or zinc ions. The TMS/ethyl mercury-induced signal of the calcium probes Fluo-4 and FURA-2 was completely absent when the zinc chelator TPEN [N,N,N',N'-tetrakis-(2-pyridyl-methyl)ethylenediamine] was added. In contrast, the signal caused by thapsigargin-induced release of calcium from the endoplasmic reticulum was unaffected by TPEN. In light of these observations, zinc may also contribute to calcium signals caused by mercury-containing compounds other than TMS, and a potential involvement of zinc release in the immunomodulatory effects of these substances should be considered.
authors.affiliation: Institute of Immunology, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany.
authors.forename: Hajo
authors.initials: H
authors.lastname: Haase
authors.forename: Silke
authors.initials: S
authors.lastname: Hebel
authors.forename: Gabriela
authors.initials: G
authors.lastname: Engelhardt
authors.forename: Lothar
authors.initials: L
authors.lastname: Rink
mesh_terms: D020013:Calcium Signaling / Q000187:drug effects*; D005021:Ethylamines / Q000494:pharmacology; D005035:Ethylmercury Compounds / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007477:Ions; D019169:Jurkat Cells; D008214:Lymphocytes / Q000378:metabolism*; D011725:Pyridines; D011743:Pyrimidines / Q000494:pharmacology; D012459:Salicylates / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D005021:Ethylamines; D005035:Ethylmercury Compounds; D005456:Fluorescent Dyes; D007477:Ions; C511824:N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine; D011725:Pyridines; D011743:Pyrimidines; D012459:Salicylates; D013438:Sulfhydryl Compounds; D013849:Thimerosal; D019284:Thapsigargin; C441201:thiosalicylic acid; D015032:Zinc