title: [Fractionation of fragments of skeletal muscle sarcoplasmic reticulum according to their sensitivity to caffeine].
abstract: Sarcoplasmic reticulum fragments were fractionated according to the ability of caffeine to selectively block Ca2+ uptake in the population of caffeine-sensitive membranes. The membrane suspension was loaded with calcium in the presence of oxalate, Mg-ATP and caffeine, after which the Ca2+-loaded caffeine-sensitive fragments were separated by sucrose density gradient centrifugation. In Ca2+-unloaded fragments of the supernatant, the sensitivity to caffeine estimated by its ability to diminish the rate of Ca2+ uptake, Ca/ATP ratio and Ca-oxalate capacity amounted to 91-93%. The terms of protein composition, the caffeine-sensitive fragments were identified with terminal cystern membranes, while the caffeine-insensitive ones with the SR canalicular membranes. The sensitivity to caffeine may serve as a reliable criterion for estimating the relative content of terminal cystern fragments in different microsomal preparations.
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000032:analysis / Q000378:metabolism; D009132:Muscles / Q000032:analysis* / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000032:analysis* / Q000378:metabolism
chemical_list: D002110:Caffeine; D002118:Calcium
vernacular_title: Fraktsionirovanie fragmentov sarkoplazmaticheskogo retikuluma skeletnoĭ myshtsy po ikh chuvstvitel'nosti k kofeinu.