title: Redox regulation of calcium release in skeletal and cardiac muscle.
abstract: In skeletal and cardiac muscle cells, specific isoforms of the Ryanodine receptor channels mediate Ca2+ release from the sarcoplasmic reticulum. These channels are highly susceptible to redox modifications, which regulate channel activity. In this work, we studied the effects of Ca2+ (endogenous agonist) and Mg2+ (endogenous inhibitor) on the kinetics of Ca2+ release from sarcoplasmic reticulum vesicles isolated from skeletal or cardiac mammalian muscle. Native skeletal vesicles exhibited maximal stimulation of release kinetics by 10-20 microM [Ca2+], whereas in native cardiac vesicles, maximal stimulation of release required only 1 microM [Ca2+]. In 10 microM [Ca2+], free [Mg2+] < 0.1 mM produced marked inhibition of release from skeletal vesicles but free [Mg2+] < or = 0.8 mM did not affect release from cardiac vesicles. Incubation of skeletal or cardiac vesicles with the oxidant thimerosal increased their susceptibility to stimulation by Ca2+ and decreased the inhibitory effect of Mg2+ in skeletal vesicles. Sulfhydryl-reducing agents fully reversed the effects of thimerosal. The endogenous redox species, glutathione disulfide and S-nitrosoglutathione, also stimulated release from skeletal sarcoplasmic reticulum vesicles. In 10 microM [Ca2+], 35S-nitrosoglutathione labeled a protein fraction enriched in release channels through S-glutathiolation. Free [Mg2+] 1 mM or decreasing free [Ca2+] to the nM range prevented this reaction. Possible physiological and pathological consequences of redox modification of release channels on Ca2+ signaling in heart and muscle cells are discussed.
authors.affiliation: Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Casilla 70005, Santiago 7, Chile. chidalgo@machi.med.uchile.cl
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hidalgo
authors.forename: Paula
authors.initials: P
authors.lastname: Aracena
authors.forename: Gina
authors.initials: G
authors.lastname: Sanchez
authors.forename: Paulina
authors.initials: P
authors.lastname: Donoso
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D004285:Dogs; D019803:Glutathione Disulfide / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010084:Oxidation-Reduction; D011310:Preservatives, Pharmaceutical / Q000494:pharmacology; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D026422:S-Nitrosoglutathione / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D013849:Thimerosal / Q000494:pharmacology
chemical_list: D020030:Nitric Oxide Donors; D011310:Preservatives, Pharmaceutical; D019837:Ryanodine Receptor Calcium Release Channel; D013849:Thimerosal; D026422:S-Nitrosoglutathione; D008274:Magnesium; D002118:Calcium; D019803:Glutathione Disulfide