Characterization of the tetraphenylboron-induced calcium release from skeletal sarcoplasmic reticulum.
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 6-8 s-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.
Soler
F
F
Departamento de Bioquimica y Biologia Molecular, Universidad de Murcia, Spain.
Fernandez-Belda
F
F
Gomez-Fernandez
J C
JC
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D007700:Kinetics; D008861:Microsomes / Q000502:physiology; D009132:Muscles / Q000378:metabolism; D010743:Phospholipids / Q000302:isolation & purification; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D013775:Tetraphenylborate / Q000494:pharmacology*
D001896:Boron Compounds; D010743:Phospholipids; D013775:Tetraphenylborate; D000252:Calcium-Transporting ATPases; D002118:Calcium