title: Role of ERK1/2 in uterine contractility and preterm labor in rats.
abstract: The present study tested the hypothesis that ERK activation is an essential step in the onset of labor in a rat model of preterm labor. The administration of RU-486, an antiprogesterone agent, to rats induced preterm delivery 22.2 +/- 0.24 h after treatment. Changes in basal signaling events were studied in myometrial tissue from CO(2)-euthanized rats. Rats treated with RU-486 displayed a dramatically increased in vitro uterine contractility compared with gestational stage-matched, sham-treated rats. In vitro contractility was not significantly different from that during spontaneous labor. During RU-486-induced preterm labor, as previously described for spontaneous labor, ERK phosphorylation levels increased, as did phosphorylation of caldesmon at Ser(789), an ERK phosphorylation site. Also, a small but significant increase in 20-kDa myosin light chain phosphorylation was seen at a constant intracellular pCa of 7. When rats were chronically treated with an agent that prevents ERK activation, U-0126, the onset of RU-486-induced preterm labor was delayed in a statistically significant manner. Chronic in vivo treatment with U-0126 also significantly inhibited the RU-486-induced increase in in vitro contractility and ERK and caldesmon phosphorylation but did not alter the RU-486-induced increase in 20-kDa myosin light chain phosphorylation. These data indicate that ERK activation is a component of the multiple events leading to the development of labor in this rat model. We suggest that the ERK pathway could possibly be used to identify targets for the development of a novel class of tocolytic agents.
authors.affiliation: Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston 02215, USA. yli1@bidmc.harvard.edu
authors.forename: Yunping
authors.initials: Y
authors.lastname: Li
authors.forename: Hyun-Dong
authors.initials: HD
authors.lastname: Je
authors.forename: Sabah
authors.initials: S
authors.lastname: Malek
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Morgan
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D020567:Fetal Weight; D006727:Hormone Antagonists / Q000494:pharmacology; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D015735:Mifepristone / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009215:Myometrium / Q000201:enzymology; D018994:Myosin Light Chains / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014590:Uterine Contraction / Q000502:physiology*; D014599:Uterus / Q000502:physiology*
chemical_list: D002070:Butadienes; D002148:Calmodulin-Binding Proteins; D004791:Enzyme Inhibitors; D006727:Hormone Antagonists; D018994:Myosin Light Chains; D009570:Nitriles; C113580:U 0126; D015735:Mifepristone; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases