Abstract

HIDALGO, CECILIA; ARACENA, PAULA; SANCHEZ, GINA  and  DONOSO, PAULINA. Redox regulation of calcium release in skeletal and cardiac muscle. Biol. Res. [online]. 2002, vol.35, n.2, pp.183-193. ISSN 0716-9760.  http://dx.doi.org/10.4067/S0716-97602002000200009.

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 µM [Ca²⁺], whereas in native cardiac vesicles, maximal stimulation of release required only 1 µM [Ca²⁺]. In 10 µM [Ca²⁺], free [Mg²⁺] < 0.1 mM produced marked inhibition of release from skeletal vesicles but free [Mg²⁺] ­ 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 µM [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

Keywords : Redox state; Ryanodine receptors; sarcoplasmic reticulum; calcium release kinetics; Mg²⁺ inhibition; S-nitrosoglutathione.