RAPID KINETIC-STUDIES OF SH OXIDATION-INDUCED CALCIUM-RELEASE FROM SARCOPLASMIC-RETICULUM VESICLES

We studied the kinetics of calcium release induced by SH oxidation in triads isolated from frog and rabbit skeletal muscle by measuring calc ium fluxes by a fast filtration method. In both species SH oxidation i nduced release of 70-80% of the passively loaded calcium with a rate c onstant of 1 s(-1). This rate constant is 3 times higher than the rate constant of calcium-induced calcium release and 15 times lower than t he rate constant of ATP-induced release. Calcium release induced by SH oxidation exhibited the same calcium dependence of calcium-induced ca lcium release and was also inhibited by physiological [Mg2+]. Neither SH oxidation-induced calcium release nor calcium-induced calcium relea se were regulated by luminal calcium. The redox state of thiol groups does not seem to control ATP-induced calcium release since the rate co nstant of calcium release after SH oxidation was not different from th e rate constant measured in the presence of the reducing agent dithiot hreitol. Our results do not support a role for SH oxidation, per se, a s an essential step for the release of calcium from sarcoplasmic retic ulum. (C) 1997 Academic Press.