Characterization of the tetraphenylboron‐induced calcium release from skeletal sarcoplasmic reticulum

Abstract

Release of Ca2+ from skeletal sarcoplasmic reticulum vesicles was studied by the spectrophotometric stopped‐flow technique using tetraphenylboron as a releasing agent. The extent of Ca2+ release shows a sigmoidal response, with respect to the tetraphenylboron concentration, being dependent on Ca2+ preloading and Ca2+ ATPase activity, since these experiments were performed on actively loaded vesicles.The release process has a rapid component with an apparent rate constant of 6–8s−1, showing a linear relationship between the rapid rate of Ca2+ release and the Ca2+ content of the vesicles. The release is not mediated by the reversal of the Ca2+ pump. Since the amphipathic anion tetraphenylboron was unable to elicit a Ca2+‐release response when added to a preparation of sarcoplasmic reticulum phospholipid vesicles, it is suggested that there may be an interaction with some membrane protein(s) at the hydrophobic/hydrophilic interface leading to the opening of some specific Ca2+‐release pathway. Copyright © 1989, Wiley Blackwell. All rights reserved