title: Hormonal control of uterine contraction. Characterization od cyclic AMP-dependent membrane properties in the myometrium.
abstract: A mitochondria-free membrane fraction prepared from rat myometrium accumulated 45Ca2+ in the presence of oxalic acid and ATP. The rate of transport of Ca2+ into the membranous vesicles was increased by greater than 50% in the presence of 3',5'-cyclic AMP, but not by 2',3'-cyclic AMP or 5'AMP. Membrane ATPase activity was stimulated by Mg2+; slight additional stimulation was obtained in the presence of Na+ and K+ but not in the presence of Ca+2. Despite the cyclic AMP sensitivity of membrane ATPase activity, the absence of any effect of inhibitors of Ca2+-transport suggest it has little to do with Ca2+ accumulation by the membranes. Cyclic AMP-induced increase in Ca2+-transport and membrane ATPase activity was duplicated in vivo by incubating uteri in 10(-4)M isoproterenol prior to membrane isolation. Isoproterenol has been previously shown to increase myometrial cyclic AMP levels, and changes in Ca2+-transport by cell membranes in relation to intracellular cyclic AMP levels may be the mechanism through which hormones modulate uterine contractility.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002369:Castration; D000242:Cyclic AMP / Q000494:pharmacology*; D004789:Enzyme Activation; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008566:Membranes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010070:Oxalates / Q000494:pharmacology; D051381:Rats; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000378:metabolism*
chemical_list: D010070:Oxalates; D010042:Ouabain; D000242:Cyclic AMP; D000251:Adenosine Triphosphatases; D008274:Magnesium; D007545:Isoproterenol; D002118:Calcium