title: Agonist-specific compartmentation of cGMP action in myometrium.
abstract: Nitric oxide relaxes myometrium in a cGMP-independent manner. Although cGMP activates its cognate kinase, this is not required for the inhibitory effect of nitric oxide. Thus, nitric oxide-mediated cGMP elevation does not enjoy the same set of substrates as it does in other smooth muscles. To further understand the regulation of relaxation of uterine muscle by cGMP, we have studied the actions of peptide-mediated cGMP action in guinea pig myometrium. We used both functional and biochemical studies of the action of the particulate guanylyl cyclase activator uroguanylin and its receptor, particulate guanylyl cyclase type C, to address the relationship between cGMP elevation acting in the membrane signaling domain to that of the nonmembrane region of the cell. Uroguanylin relaxed oxytocin-induced contractions in a dose-dependent fashion only in pregnant myometrium. Both relaxation and cGMP accumulation after uroguanylin stimulation were blocked by the putative particulate guanylyl cyclase type C inhibitors 2-chloro-ATP and isatin (1H-indole-2,3-dione), but not by the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-A]quinoxalin-1-one (ODQ). Uroguanylin stimulated cGMP accumulation only in the pregnant myometrium. Caveolin-1 expression increased in pregnancy toward term. In the caveolin-1-containing membrane domain, uroguanylin, but not the nitric-oxide donor, led to the elevation of cGMP that was insensitive to ODQ. Particulate guanylyl cyclase C was expressed and prouroguanylin was detected in pregnant myometrium. We conclude that a uroguanylin-particulate cyclase-cGMP relaxation pathway is present and cGMP is compartmented in myometrium. The agonist-mediated selectivity of relaxation to cGMP is of fundamental pharmacological interest in understanding signal transduction in smooth muscle.
authors.affiliation: Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA. ibuxton@medicine.nevada.edu
authors.forename: Iain L O
authors.initials: IL
authors.lastname: Buxton
authors.forename: Deanna
authors.initials: D
authors.lastname: Milton
authors.forename: Scott D
authors.initials: SD
authors.lastname: Barnett
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Tichenor
mesh_terms: D000818:Animals; D015153:Blotting, Western; D051242:Caveolin 1 / Q000096:biosynthesis; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006152:Cyclic GMP / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006017:Glycolipids / Q000378:metabolism; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D009215:Myometrium / Q000187:drug effects*; D045265:Natriuretic Peptides / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011247:Pregnancy; D011810:Quinoxalines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D051242:Caveolin 1; D004791:Enzyme Inhibitors; D004967:Estrogens; D006017:Glycolipids; D045265:Natriuretic Peptides; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011810:Quinoxalines; C084362:uroguanylin; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D006152:Cyclic GMP