[Release of Ca2+ ions from the sarcoplasmic reticulum of skeletal muscle induced by heparin. Relation between the Ca2+ release caused by Ca2+ ions and caffeine].
Using a Ca2+-selective electrode and Quin 2 and chlortetracycline fluorescence, a Ca2+ release from terminal cysterns of skeletal muscle sarcoplasmic reticulum under effects of heparin, caffeine and Ca2+ has been studied. It was shown that Ca2+ release induced by heparin is insensitive to the blockers of Mg2+-dependent system of Ca2+-induced Ca2+ release, i.e., Mg2+, tetracaine and dimethylsulfoxide. Preliminary release of Ca2+ in the presence of caffeine, which activates Mg2+-dependent Ca2+ release, does not prevent the heparin-induced Ca2+ release. At the same time, after Ca2+ release caused by Ca2+ in a Mg2+-independent system, heparin cannot cause additional efflux of Ca2+. It has been shown that the heparin-induced release of Ca2+ diminishes with a decrease in a decrease in Ca2+ concentration. This effect is less pronounced in the presence of Na+ than with K+. The data obtained suggest that sarcoplasmic reticulum terminal cysterns contain two systems of Ca2+-induced release of Ca2+, i.e., a Mg2+-dependent, caffeine-sensitive and a Mg2+-independent heparin-sensitive ones. The mechanism of activation of both systems by caffeine and heparin consists, in all probability, in their increased affinity for Ca2+.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D005456:Fluorescent Dyes; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D005456:Fluorescent Dyes; D007473:Ion Channels; D002110:Caffeine; D006493:Heparin; D002118:Calcium
Osvobozhdenie ionov Ca2+ iz sarkoplazmaticheskogo retikuluma skeletnykh myshts pod deĭstviem geparina. Sviaz' s osvobozhdeniem Ca2+ pod deĭstviem ionov Ca2+ i kofeina.