[Effect of cAMP-dependent phosphorylation on the activity of Mg2+,Ca2+-ATP-ase and Ca2+ transport in the sarcoplasmic reticulum of the white skeletal muscles of the rabbit]. / Vliianie cAMP-zavisimogo fosforilirovaniia na aktivnost' Mg2+,Ca2+-ATP-azy i transport Ca2+ v sarkoplazmaticheskom retikulume belykh skeletnykh myshts krolika.

It is shown that endogenic phosphorylation of sarcoplasmatic reticulum membranes in white skeletal muscles of rabbit stimulates Mg2+, Ca2+-ATPase activity and Ca2+ accumulation. When the level of endogenic phosphorylation is high, exogenic cAMP and protein kinase do not affect Mg2+, Ca2+-ATPase activity, when the level is low, they produce a 1.5-2-fold increase in the activity. The inhibitor of cAMP-dependent protein kinase practically completely eliminates the effect of endogenic phosphorylation on Ca2+ accumulation and Mg2+, Ca2+-ATPase activity. Under endogenic phosphorylation the Ca2+ binding constant becomes 1.8 times as low in sites of high affinity for this ion, and 4 times as low--in sites of low affinity.

[Physicochemical characteristics of calcium binding with plasma membranes of rabbit skeletal muscles]. / Fiziko-khimichni kharakteristiki zv'iazuvannia kal'tsiiu plazmatichnimi membranami skeletnikh m'iaziv krolia.

It is established that Ca2+ binding with rabbit skeletal muscles plasmatic membrane depends on this cation concentration in the incubating medium. pH, temperature, incubation period and presence of Mg ions in the medium affect the Ca2+-binding ability of sarcolemma. The entropic changes observed in sarcolemma Ca2+ binding are due to conformation reconstructions of the membrane components.