Heavy metals induce rapid calcium release from sarcoplasmic reticulum vesicles isolated from skeletal muscle.

Micromolar concentrations of mercury, silver, and other reagents known to react with sulfhydryl groups are shown to stimulate ATPase activity and inhibit active calcium uptake in sarcoplasmic reticulum vesicles derived from rabbit fast skeletal muscle. These effects are caused by a dramatic increase in the calcium permeability of the sarcoplasmic reticulum. Measurements of Ca2+ permeability were made using both isotopes and by spectrophotometric techniques using the Ca2+ indicator arsenazo III. Air oxidation of a sulfhydryl group to a disulfide group also leads to a large increase in the calcium permeability of the sarcoplasmic reticulum.