title: A comparative study of vascular responsiveness of myometrial and omental small resistance arteries in late-gestation sheep.
abstract: OBJECTIVE
  We determined whether local regulation by vasoactive agents differs in the myometrial and omental vascular beds in the pregnant sheep. Specifically, we hypothesized that there would be blunting of in vitro responses to constrictor agonists, enhancement of sensitivity to dilator agonists, or both in myometrial compared with omental resistance arteries.
  
  
  METHODS
  We compared in vitro responsiveness of small resistance intramyometrial and omental arteries from near-term pregnant ewes to the vasoconstrictor agents norepinephrine, U46619 (a thromboxane sympathomimetic), and potassium and the vasodilator agents acetylcholine and bradykinin.
  
  
  RESULTS
  The vascular sensitivity and the maximum response of intramyometrial small arteries to U46619 was attenuated compared with that of omental arteries. There were no significant differences between the intramyometrial and omental arteries in response to norepinephrine, potassium, acetylcholine, or bradykinin.
  
  
  CONCLUSIONS
  These results support regional heterogeneity of regulation of function in different maternal vascular beds during pregnancy. The relative insensitivity of the myometrial arteries to the thromboxane mimetic indicates the existence of decreased constrictor function that may facilitate preservation of uterine blood flow in vivo.
authors.affiliation: Laboratory for Pregnancy, Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Anwar
authors.forename: C
authors.initials: C
authors.lastname: Docherty
authors.forename: L
authors.initials: L
authors.lastname: Poston
authors.forename: P W
authors.initials: PW
authors.lastname: Nathanielsz
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000187:drug effects* / Q000502:physiology*; D001920:Bradykinin / Q000494:pharmacology; D005260:Female; D005865:Gestational Age; D009215:Myometrium / Q000098:blood supply*; D009638:Norepinephrine / Q000494:pharmacology; D009852:Omentum / Q000098:blood supply*; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D012756:Sheep; D014655:Vascular Resistance; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000109:Acetylcholine; D011188:Potassium; D001920:Bradykinin; D009638:Norepinephrine