The Ca2+ release channel in junctional sarcoplasmic reticulum: gating and blockade by cations.
1. By using a sarcoplasmic reticulum preparation containing feet structures and the 45Ca2+/filtration technique, the opening and closing response of the Ca(2+)-channel was studied. 2. Extravesicular Sr2+ can activate the channel even though this cation is less efficient than Ca2+ in stimulating the Ca2+ release. Higher Sr2+ concentrations display inhibitory action. 3. By studying the closing response high- and low-affinity cations can be distinguished, according to the concentration range required to exert their effect. 4. The synergistic behavior observed by combining high- and low-affinity blocking cations suggest that they interact through the same binding site. 5. The high-and low-affinity cations are noncompetitive blockers of the activating Ca2+ suggesting the existence of an inhibitory site which is different to the activating site.
Soler
F
F
Departamento de Bioquimica y Biologia Molecular, Facultad de Veterinaria, Universidad de Murcia, Spain.
Fernandez-Belda
F
F
Gomez-Fernandez
J C
JC
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007365:Intercellular Junctions / Q000378:metabolism*; D015640:Ion Channel Gating; D007811:Lanthanum / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D011817:Rabbits; D012430:Ruthenium Red / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002412:Cations; D012430:Ruthenium Red; D007811:Lanthanum; D008274:Magnesium; D002118:Calcium