Modifications of Ca2+ transport induced by glutathione in sarcoplasmic reticulum membranes of frog skeletal muscle.

The Ca2+ transport across the membrane of vesicles purified from the sarcoplasmic reticulum (SR) of frog skeletal muscle is modified by raising the concentration of the reduced form of glutathione (GSH). Passive release of Ca2+ is inhibited through the direct action of GSH on ryanodine receptors while active uptake is increased by a dose-dependent stimulation of Ca2+ pumps (Ca2+ -ATPase). These effects are physiological since the concentrations of GSH utilised (0.01-10.0 mM) are compatible with the in vivo concentration of this antioxidant. They are independent of the external Ca2+ concentration and are specific for the reduced form of glutathione, since the disulphide form (GSSG) or other GSH-derivatives do not induce these effects.