title: Regulation of cGMP-induced relaxation and cGMP-dependent protein kinase in rat myometrium during pregnancy.
abstract: Increases in guanosine 3',5'-cyclic monophosphate (cGMP) induced by nitric oxide (NO), nitrovasodilators, and atrial peptides correlate with relaxation of vascular smooth muscle. Relaxation of myometrial smooth muscle by increases in cGMP, however, has required unusually high concentrations of the cyclic nucleotide. We tested the hypothesis that the sensitivity of myometrium to relaxation by cGMP is increased during pregnancy. Aortic smooth muscle was more sensitive to relaxation by cGMP than myometrial tissues, and, contrary to our hypothesis, myometrium from pregnant rats was least sensitive. Although levels of cGMP were elevated after treatment with the NO donor, S-nitroso-N-acetylpenicillamine, relaxation of myometrial tissues obtained from pregnant rats occurred only at extraordinarily high concentrations. The levels of cGMP-dependent protein kinase (PKG) were significantly decreased in myometrium from pregnant rats compared with myometrium from nonpregnant cycling animals or aortic smooth muscle. Administration of estradiol to ovariectomized rats increased myometrial PKG expression, and progesterone antagonized this response. We conclude that 1) myometrial tissues from pregnant rats are not sensitive to relaxation by cGMP and 2) this insensitivity to cGMP is accompanied by progesterone-mediated decreases in the level of PKG expression.
authors.affiliation: Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235-9032, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Word
authors.forename: T L
authors.initials: TL
authors.lastname: Cornwell
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D015536:Down-Regulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism; D009126:Muscle Relaxation; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D009215:Myometrium / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism; D010052:Ovariectomy; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D026423:S-Nitroso-N-Acetylpenicillamine
chemical_list: D004791:Enzyme Inhibitors; D010726:Phosphodiesterase Inhibitors; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D017869:Cyclic GMP-Dependent Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006162:Guanylate Cyclase; D010396:Penicillamine; D006152:Cyclic GMP