title: [cAMP-dependent regulation of the active transport of Ca2+ in plasma membranes of the swine myometrium].
abstract: Plasma membranes of pig myometrium show the ability for endogenous phosphorylation (160 +/- 45 pmol 32P/mg.min); the initial rate of this process increases 2.5-fold in the presence of 10(-6) cAMP. Micromolar concentrations of cAMP activate the ATP-dependent transport of Ca2+ in myometrium plasma membranes; cAMP at concentrations of 10(-9)-10(-4) M has no effect on Ca,Mg-ATPase. Myometrium plasma membranes possess the Mg2+-dependent phosphatase activity. Dephosphorylation of membranes is accompanied by a decrease (by 25-50%) of the Ca,Mg-ATPase activity and Ca2+ uptake, respectively. The exogenous catalytic subunit of cAMP-dependent protein kinase increases the activity of Ca,Mg-ATPase in native and dephosphorylated membranes. Tolbutamide diminishes the activity of Ca,Mg-ATPase in native membranes by 25% without causing any appreciable influence on the enzyme activity in dephosphorylated membranes. Taking into account the similarity of dependence of Ca2+ uptake on Ca2+ concentration in native and cAMP-phosphorylated vesicles, it can be assumed that the cAMP-dependent phosphorylation affects the enzyme turnover number but not its affinity for Ca2+. The dephosphorylation-induced inhibition of Ca,Mg-ATPase activity and accumulation of Ca2+ are reversible processes.
authors.forename: M D
authors.initials: MD
authors.lastname: Kurskiĭ
authors.forename: T P
authors.initials: TP
authors.lastname: Kondratiuk
authors.forename: L G
authors.initials: LG
authors.lastname: Babich
authors.forename: S F
authors.initials: SF
authors.lastname: Bychenok
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology*; D005260:Female; D007700:Kinetics; D009215:Myometrium / Q000378:metabolism*; D010766:Phosphorylation; D013552:Swine
chemical_list: D000242:Cyclic AMP; D002118:Calcium
vernacular_title: cAMP-zavisimaia reguliatsiia aktivnogo transporta Ca2+ v plazmaticheskikh membranakh miometriia svin'i.