title: Guanine nucleotide binding in human placental syncytiotrophoblast membranes and comparative regulation of adenylate cyclase in syncytiotrophoblast, turkey erythrocyte and bovine calf testes membranes by guanosine-5'-triphosphate.
abstract: Guanosine-5'-triphosphate (GTP) binds specifically to syncytiotrophoblast plasma membranes and increases the production of cyclic AMP in these membranes. 1. In syncytiotrophoblast membranes, GTP alone caused a significant increase in the basal levels of cyclic AMP in a dose dependent manner. 2. GTP alone did not significantly stimulate cyclic AMP production in turkey erythrocyte or bovine calf testes membranes. 3. GTP decreased Gpp(NH)p-mediated cyclic AMP production while increasing NaF-mediated cyclic AMP production in placental, erythrocyte and testes membranes. 4. Since cyclic AMP has been reported to regulate the levels of placental hormones, and it is shown in this study that GTP increases cyclic AMP production in the placenta, this study suggests: (A) placental GTP levels may indirectly regulate placental hormone production, (B) placental beta adrenergic (BA) mediated adenylate cyclase activity may not be regulated in the same manner as the BA system of avian erythrocytes.
authors: Department of Biochemistry, Albany Medical College of Union University, NY 12208.
authors: L W
authors: LW
authors: Figgs
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004912:Erythrocytes / Q000201:enzymology*; D006150:Guanine Nucleotides / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000201:enzymology; D010920:Placenta / Q000166:cytology; D013737:Testis / Q000201:enzymology*; D014327:Trophoblasts / Q000378:metabolism*; D014422:Turkeys
chemical_list: D006150:Guanine Nucleotides; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D000262:Adenylyl Cyclases; D007545:Isoproterenol