title: Prostaglandin E2 activates phospholipase C and elevates intracellular calcium in cultured myometrial cells: involvement of EP1 and EP3 receptor subtypes.
abstract: PGE2 is a powerful modulator of uterine contractility, but there is uncertainty as to which receptor subtypes (EP1, EP2, EP3, or EP4), G proteins, and second messenger systems are activated by PGE2 in myometrium. Here we show that in cultured human myometrial cells, PGE2 (1-100 microM) activates phospholipase C (PLC) up to 500% over the control level and elevates intracellular calcium ([Ca2+]i) from the resting level of 60-90 nM up to 350 nM in a concentration-dependent manner. Stimulation by the receptor subtype-selective analogs GR63799X (EP3), sulprostone (EP3 > EP1), and misoprostol (EP3 > EP2 > EP1) indicates that these effects are transmitted through EP3 receptors. Both effects are resistant to pertussis toxin (PT). Lower concentrations of PGE2 (1-300 nM) increase [Ca2+]i via a PT-sensitive pathway, without PLC activation. This [Ca2+]i increase occurs after an inverse dose-related delay and is inhibited by the selective EP1 antagonist AH6809 and calcium channel blockers. By comparison, oxytocin stimulates PLC up to 1000% over the control level and elevates [Ca2+]i up to 800 nM in a concentration-dependent manner without any measurable delay; both effects are partly sensitive to PT. These data provide functional evidence for the presence of different stimulatory mechanisms for PGE2 in myometrium: 1) a low affinity receptor (probably EP3D) that activates PLC through a PT-insensitive pathway; and 2) a high affinity receptor (probably EP1), independent from PLC and involving a PT-sensitive G protein (G(i)?). Both pathways lead to elevation of [Ca2+]i.
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Headington, United Kingdom. gergely.asboth@obstetrics-gynaecology.oxford.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Asbóth
authors.forename: S
authors.initials: S
authors.lastname: Phaneuf
authors.forename: G N
authors.initials: GN
authors.lastname: Europe-Finner
authors.forename: M
authors.initials: M
authors.lastname: Tóth
authors.forename: A L
authors.initials: AL
authors.lastname: Bernal
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000494:pharmacology; D037342:Pertussis Toxin; D011459:Prostaglandins E, Synthetic / Q000494:pharmacology; D018078:Receptors, Prostaglandin E / Q000502:physiology*; D058306:Receptors, Prostaglandin E, EP1 Subtype; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; C545635:PTGER1 protein, human; D011459:Prostaglandins E, Synthetic; D018078:Receptors, Prostaglandin E; D058306:Receptors, Prostaglandin E, EP1 Subtype; D010566:Virulence Factors, Bordetella; D010121:Oxytocin; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D015232:Dinoprostone; D002118:Calcium