title: Synthesis of adenosine triphosphate during release of intravesicular and membrane-bound calcium ions from passively loaded sarcoplasmic reticulum.
abstract: Sarcoplasmic reticulum isolated from rabbit skeletal muscle and incubated in a medium containing Ca2+ in the absence of ATP retains intravesicular and/or membrane-bound Ca2+. The synthesis of ATP coupled with the release of intravesicular Ca2+ is totally inhibited by the ionophore X-537A. Release of the membrane-bound Ca2+, retained after short periods of incubation (10min) or after release of the intravesicular Ca2+ by ionophore X-537A, still supports some synthesis of ATP. The ratios of Ca2+ released to ATP synthesized are 2.5-3.2, when bound and intravesicular Ca2+ are released simultaneously, and 3.1-4.0, when only bound Ca2+ is released. The results show that the synthesis of ATP by sarcoplasmic reticulum during release of passively accumulated Ca2+ by EGTA [ethanedioxybis(ethylamine)tetra-acetic acid] is accompanied by a loss of membrane-bound Ca2+.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007832:Lasalocid / Q000494:pharmacology; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004533:Egtazic Acid; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002118:Calcium; D007832:Lasalocid