title: Oxidized glutathione causes sensitization of calcium release to inositol 1,4,5-trisphosphate in permeabilized hepatocytes.
abstract: The effects of GSSG on Ca2+ mobilization by Ins(1,4,5)P3 were studied in permeabilized rat hepatocytes. Incubation with GSSG (2 mM) increased the sensitivity to Ins(1,4,5)P3 for Ca2+ release, with no effect on the size of the Ca2+ pool that could be released with maximal concentrations of Ins(1,4,5)P3. GSSG decreased the EC50 for Ins(1,4,5)P3 from a control value of 578 +/- 23 nM to 137 +/- 21 nM. GSSG had no effect on the metabolism of Ins(1,4,5)P3 in permeabilized cells, and sensitization of Ca2+ release was still observed when the poorly metabolizable analogue inositol 1,4,5-trisphosphorothioate was used. GSSG did not affect the ATP-dependent Ca2+ pump or the extent of loading of intracellular Ca2+ pools. In addition, the enhancement of Ins(1,4,5)P3-sensitivity by GSSG occurred under conditions where the Ca2+ pumps were blocked with thapsigargin or by chelation of medium Ca2+ just before Ins(1,4,5)P3 addition. The effect of GSSG was time- and dose-dependent, maximal effects being observed after 5 min incubation with 2 mM-GSSG. Cystine mimicked the GSSG-induced increase in Ins(1,4,5)P3-sensitivity, and the effects could be reversed by dithiothreitol (DTT). DTT, GSH glutathione and cysteine had no effect when added alone. Other agents known to react with protein thiols, including N-ethylmaleimide, p-chloromercuribenzoic acid and Ag+, did not affect the sensitivity to Ins(1,4,5)P3, but were inhibitors of ATP-dependent Ca2+ uptake. The data suggest that the sensitivity of the intracellular Ca2+ pools to release by Ins(1,4,5)P3 can be modulated by the formation of mixed disulphides with GSSG or other oxidized thiols.
authors.affiliation: Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107.
authors.forename: D C
authors.initials: DC
authors.lastname: Renard
authors.forename: M B
authors.initials: MB
authors.lastname: Seitz
authors.forename: A P
authors.initials: AP
authors.lastname: Thomas
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002412:Cations; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002729:Chloromercuribenzoates / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D012834:Silver / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology
chemical_list: D002412:Cations; D002729:Chloromercuribenzoates; D013438:Sulfhydryl Compounds; D012834:Silver; D015544:Inositol 1,4,5-Trisphosphate; D005978:Glutathione; D005033:Ethylmaleimide; D002118:Calcium