title: The effects of methyl palmitate, a putative regulator from perivascular fat, on the contractility of pregnant human myometrium.
abstract: OBJECTIVE
  Methyl palmitate is thought to cause relaxation in vascular smooth muscle by opening voltage-activated potassium channels. We have tested the hypothesis that methyl palmitate, a putative regulator from perivascular fat, is an inhibitor of the contractility of human pregnant myometrium and that its effects might partially explain the higher incidence of dysfunctional labor in obese women compared to those with normal body mass indices.
  
  
  METHODS
  Strips of myometrium obtained with informed consent from women undergoing elective cesarean section at term were mounted in organ baths. Strips stimulated with oxytocin (1nM) or KCl (30mM) were exposed to cumulatively increasing concentrations of methyl palmitate up to 10μM. Similar strips were exposed to cumulative addition of the potassium channel blockers 4-aminopyridine and tetraethylammonium. The contractility of the strips was monitored and analyzed using conventional methods.
  
  
  RESULTS
  Methyl palmitate failed to inhibit oxytocin- or KCl-induced contractions over the concentration range tested. In fact, it exerted a slight excitatory effect in the presence of KCl, though not in the presence of oxytocin. The contractility of naïve strips was unaltered by exposure to 1μM methyl palmitate. Both 4-aminopyridine and tetraethylammonium produced concentration-dependent contractions of human pregnant myometrium providing pharmacological evidence for the presence of voltage-activated potassium channels in this preparation.
  
  
  CONCLUSIONS
  Our findings do not support the hypothesis that methyl palmitate is an inhibitor of human pregnant myometrial contractility. Alternate hypotheses must be pursued to explain the higher incidence of dysfunctional labor in obese women.
authors.affiliation: Department of Obstetrics and Gynaecology, National University of Ireland Galway, Galway, Ireland. Electronic address: cranksha@mcmaster.ca.
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Crankshaw
authors.affiliation: Department of Obstetrics and Gynaecology, National University of Ireland Galway, Galway, Ireland.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Walsh
authors.affiliation: Department of Obstetrics and Gynaecology, National University of Ireland Galway, Galway, Ireland.
authors.forename: John J
authors.initials: JJ
authors.lastname: Morrison
mesh_terms: D015761:4-Aminopyridine / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism; D010120:Oxytocics / Q000494:pharmacology; D010121:Oxytocin / Q000494:pharmacology; D010168:Palmitates / Q000008:administration & dosage* / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000008:administration & dosage / Q000494:pharmacology*; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D019789:Tetraethylammonium / Q000008:administration & dosage / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects* / Q000378:metabolism
chemical_list: D010120:Oxytocics; D010168:Palmitates; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D010121:Oxytocin; D019789:Tetraethylammonium; D011189:Potassium Chloride; D015761:4-Aminopyridine; C019012:methyl palmitate
keywords: 4-Aminopyridine; Contractility; Dysfunctional labor; Methyl palmitate; Obesity; Oxytocin; Perivascular fat; Pregnant human myometrium; Tetraethylammonium; Voltage-gated potassium channels