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1Author    Wilhelm Hasselbach, Andrea MigalaRequires cookie*
 Title    Modulation by Monovalent Anions of Calcium and Caffeine Induced Calcium Release from Heavy Sarcoplasmic Reticulum Vesicles  
 Abstract    Both calcium and caffeine induced calcium release from actively loaded heavy sarcoplasmic reticulum vesicles were studied to analyze the dependence o f both activities on the com position o f the release medium with respect to monovalent anions. Calcium is unable to induce net cal­ cium release while caffeine remains effective as releasing agent when the experimental media contain neither chloride nor nitrate ions. Caffeine induced calcium release is not suppressed by chelating residual medium calcium (approximately 0 .5 -1 (j m) with 2 m M EGTA added 15 s prior to 10 m M caffeine. Calcium release from vesicles loaded in media containing 0.2 m glu­ conate as monovalent anion is induced when the medium is supplemented with chloride or nitrate. The release amplitude increases linearly when K-gluconate is replaced by KC1. At con­ stant ionic strength the release amplitude becomes maximal at a chloride concentration o f 0.2 m . The chloride effect com pletely disappears when 2 m M EGTA are added simultaneously. When chloride is replaced by nitrate, as releasing agent, maximal release is achieved already by addition o f 0.1 m K-nitrate. The releasing effect o f nitrate can only partially be suppressed by EGTA. The different effectiveness o f gluconate, chloride and nitrate as calcium release sup­ porting ions corresponds to their activating effect on the binding o f ryanodine to the calcium release channel in the vesicular membranes. 
  Reference    Z. Naturforsch. 47c, 440 (1992); received December 4 1991/March 16 1992 
  Published    1992 
  Keywords    Sarcoplasmic Reticulum, Calcium Release, Chloride, Nitrate, Ryanodine 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0440.pdf 
 Identifier    ZNC-1992-47c-0440 
 Volume    47