title: 5-hydroxytryptamine and thromboxane A2 as physiologic mediators of human umbilical artery closure.
abstract: OBJECTIVE
  This study investigated the response of the human umbilical artery to various agonists in order to determine which agents might be involved in umbilical cord closure.
  
  
  METHODS
  Umbilical artery rings from 22 cesarean deliveries were suspended in tissue baths containing Krebs-Henseleit solution under low and normal oxygen conditions. Samples were challenged with 5-hydroxytryptamine, acetylcholine, angiotensin II, bradykinin, endothelin-1, histamine, norepinephrine, phenylephrine, and U46619 (a thromboxane A(2) mimetic).
  
  
  RESULTS
  Only 5-hydroxytryptamine, bradykinin, endothelin-1, histamine, and U46619 produced appreciable maximal contractions. Furthermore, although the contractile force generated by these agonists was diminished in normal oxygen conditions, this reduction affected responses to 5-hydroxytryptamine and U46619 least.
  
  
  CONCLUSIONS
  5-Hydroxytryptamine and U46619 demonstrated the characteristics most likely to be associated with closure of the umbilical artery, ie, they elicited strong, sustained contractions at physiologic concentrations and under both normal and low-oxygen conditions. These data suggest that closure of the umbilical artery may be mediated by 5-hydroxytryptamine and thromboxane A(2).
authors.affiliation: Department of Pharmacology, The University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors.forename: Adrian
authors.initials: A
authors.lastname: Quan
authors.forename: Susan W S
authors.initials: SW
authors.lastname: Leung
authors.forename: Terence T
authors.initials: TT
authors.lastname: Lao
authors.forename: Ricky Y K
authors.initials: RY
authors.lastname: Man
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology / Q000502:physiology; D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology / Q000502:physiology; D019332:Endothelin-1 / Q000494:pharmacology / Q000502:physiology; D005260:Female; D006632:Histamine / Q000494:pharmacology / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011247:Pregnancy; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D013928:Thromboxane A2 / Q000494:pharmacology / Q000502:physiology*; D014469:Umbilical Arteries / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D019332:Endothelin-1; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D010656:Phenylephrine; D012701:Serotonin; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D006632:Histamine; D000109:Acetylcholine; D010100:Oxygen; D001920:Bradykinin; D009638:Norepinephrine