High-affinity Ca2+-binding site inhibiting Ca2+ release from sarcoplasmic reticulum.
Ca2+ release from sarcoplasmic reticulum membranes, activated by alkaline pH occurs only when EGTA is present in the release medium. Addition of very low concentrations of Ca2+ to the medium inhibits Ca2+ release. The concentration of free Ca2+ required for 50% inhibition ranges from between 5 and 20 nM in different experiments and/or membrane preparations, irrespective of whether the free Ca2+ concentration is controlled by EGTA or CDTA. Other divalent cations such as Mn2+, Ba2+, Cu2+, Cd2+ and Mg2+ also exert an inhibitory effect on Ca2+ release, with higher or lower potency than that of Ca2+. The inactivation of Ca2+ release by Ca2+ is reversible. We suggest the involvement of high-affinity Ca2+-binding sites in the control of Ca2+ release.
Argaman
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Department of Biology, Ben Gurion University of the Negev, Beer Sheva, Israel.
Shoshan-Barmatz
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D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D004533:Egtazic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012430:Ruthenium Red / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
D002413:Cations, Divalent; D012430:Ruthenium Red; D004533:Egtazic Acid; D002118:Calcium