Hormonal control of uterine contraction: Characterization of cyclic AMP-dependent membrane properties in the myometrium |
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Authors: | JFrederick Krall Janet L Swensen Stanley G Korenman |
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Institution: | Department of Medicine, UCLA San Fernando Valley Medical Program, Veterans Administration Hospital, Sepulveda, Calif. 91343 U.S.A. |
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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 cyclic AMP in a manner similar to Ca2+-transport. ATPase activity was stimulated by Mg2+; slight additional stimulation was obtained in the presence of Na+ and K+ but not in the presence of Ca2+. 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. |
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Keywords: | Cyclic AMP adenosine cyclic 3′ 5′-monophosphate EGTA Send reprint requests to: J Frederick Krall Molecular Endocrinology Laboratory Veterans Administration Hospital 16111 Plummer Street Sepulveda Calif 91343 U S A |
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