Silver ion triggers Ca2+ release from intracellular store sites in saponin-treated HL-60 cells.
We examined the effect of silver ion on Ca2+ mobilization from intracellular stores in permeabilized HL-60 cells using a filtration method and 45Ca2+. In HL-60 cells preloaded with Ca2+ in the presence of ATP, micromolar concentrations of AgNO3 elicited marked Ca2+ release within 1 min. The AgNO3-induced Ca2+ release was not affected by the free Ca2+ concentration in the medium. Equivalent concentrations of AgNO3 inhibited energy-dependent Ca2+ uptake as well as oxalate-supported Ca2+ uptake. In passive Ca2+ release experiments when ATP was completely depleted in the solution, AgNO3 also triggered Ca2+ release. Sulfhydryl protecting agents such as 2-mercaptoethanol, dithiothreitol, and glutathione (reduced form) blocked the AgNO3-induced Ca2+ release. From these results, we conclude that the apparent Ca2+ release induced by AgNO3 is mainly due to inhibition of the Ca2+ pump with increased permeability for Ca2+ and partly due to a direct effect on the Ca2+ release channel, probably by modification of sulfhydryl groups on these proteins.
Taguchi
F
F
Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Suematsu
E
E
Nishimura
J
J
Nawata
H
H
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D006098:Granulocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D012503:Saponins / Q000494:pharmacology*; D012835:Silver Nitrate / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology
D012503:Saponins; D013438:Sulfhydryl Compounds; D012835:Silver Nitrate; D002118:Calcium