title: Estrogen-induced increases in coronary blood flow are antagonized by inhibitors of nitric oxide synthesis.
abstract: OBJECTIVE
  Estrogen receptors have been found in coronary arterial endothelial and vascular smooth muscle cells. Therefore the present study was designed to determine if estradiol-17 beta can increase coronary blood flow and if so whether the changes are mediated by nitric oxide.
  
  
  METHODS
  Five oophorectomized non-pregnant sheep were chronically instrumented to measure blood pressure, heart rate, cardiac output, left circumflex coronary blood flow and central venous pressure. Animals received estradiol-17 beta (1.0 micrograms/kg) and cardiovascular responses were followed for 135 min.
  
  
  RESULTS
  Estradiol-17 beta (1.0 micrograms/kg) increased left circumflex (coronary) blood flow 28 +/- 3%, cardiac output 15 +/- 1% and heart rate by 13 +/- 3%. Coronary vascular resistance decreased 23 +/- 5%, systemic vascular resistance decreased by 12 +/- 2% while blood pressure did not change significantly. Administration of the nitric oxide synthetase inhibitor L-nitroarginine methylester (L-NAME), had no effect on basal coronary blood flow but completely reversed estradiol-17 beta induced increases in coronary blood flow.
  
  
  CONCLUSIONS
  These results demonstrate that estrogen increases coronary blood flow in the non-pregnant sheep and that L-NAME, an inhibitor of nitric oxide, is able to reverse the estrogen induced flow changes.
authors.affiliation: Zentrum für Geburtshilfe und Frauenheilkunde am Klinikum, Justus-Liebig-Universität Giessen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Lang
authors.forename: R S
authors.initials: RS
authors.lastname: Baker
authors.forename: K E
authors.initials: KE
authors.lastname: Clark
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D012756:Sheep
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D004958:Estradiol; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester