[Activation of the caffeine center of the sarcoplasmic reticulum at a reduced concentration of magnesium ions].
The action of caffeine and Mg2+ on the efficacy of Ca2+ transport by terminal cisterns and longitudinal tubules of rabbit skeletal muscle sarcoplasmic reticulum (SR) was studied and compared. Addition of 5 to 10 mM caffeine to the incubation medium or a decrease in Mg2+ concentration from 4 to 0.1 mM led to a 3-fold diminution of the Ca/ATP ratio for the terminal cistern fraction. In longitudinal tubules, that effect was far less pronounced. The effects of caffeine and decreases in Mg2+ concentration were blocked by ruthenium red, tetracaine and dimethylsulfoxide. It is assumed that the decrease in Mg2+ concentration is accompanied by activation of the caffeine site of the SR, induced by the intravesicular caffeine-like factor.
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects; D002110:Caffeine / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
D002110:Caffeine; D008274:Magnesium; D002118:Calcium
Aktivatsiia kofeinovogo tsentra sarkoplazmaticheskogo retikuluma pri snizhenii kontsetratsii ionov magniia.