Critical reevaluation of murexide technique in the measurement of calcium transport by cardiac sarcoplasmic reticulum

Calcium transport by cardiac sarcoplasmic reticulum preparations appears biphasis when measured by dual wavelength spectrophotometry with murexide, initial binding being followed by the suppposedly contingent process of “release”. We present evidence that this “release” phase is a methodological artefact due to murexide penetration into the sarcoplasmic reticulum.