title: Oestrogen increases myocardial blood flow in men: assessment by 13N-ammonia positron emission tomography.
abstract: OBJECTIVE
  Oestrogen has been shown to increase nitric oxide-mediated vasodilatation and modulate sympathetic tone in postmenopausal women. We investigated the acute effects of oestrogen on the coronary microcirculation in men.
  
  
  METHODS
  Myocardial blood flow was quantified using N-ammonia positron emission tomography before and 20 min after an intravenous administration of conjugated oestrogen (10 mg) in nine healthy men.
  
  
  RESULTS
  There were no significant changes in either systemic blood pressure or heart rate before and after oestrogen infusion. However, myocardial blood flow was increased by oestrogen from 0.88 +/-0.06 to 1.05+/-0.09 ml x g x min (P<0.05). Although serum levels of nitrite/nitrate (end products of nitric oxide) were not increased, circulating norepinephrine (noradrenaline) levels were decreased after the administration of oestrogen from 401+/-114 to 346+/-112 pg x ml (P<0.01). A significant negative correlation was found between myocardial blood flow and plasma norepinephrine levels (r=-0.67, P<0.05).
  
  
  CONCLUSIONS
  A single administration of oestrogen enhanced myocardial circulation in healthy men. The oestrogen-induced increase in myocardial blood flow may be due to direct effects on the coronary circulation or through the modulation of norepinephrine levels, rather than the production of nitric oxide.
authors.affiliation: Division of Tracer Kinetics, Osaka University Graduate School of Medicine, Osaka, Japan. jyoshioka@rics.bwh.harvard.edu
authors.forename: Jun
authors.initials: J
authors.lastname: Yoshioka
authors.forename: Shinji
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Node
authors.forename: Daisaku
authors.initials: D
authors.lastname: Nakatani
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kitakaze
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hori
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Nishimura
mesh_terms: D000328:Adult; D000641:Ammonia; D001783:Blood Flow Velocity / Q000187:drug effects*; D003326:Coronary Circulation / Q000187:drug effects*; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000187:drug effects* / Q000378:metabolism; D004967:Estrogens / Q000008:administration & dosage*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009569:Nitric Oxide / Q000097:blood; D009590:Nitrogen Radioisotopes; D009638:Norepinephrine / Q000097:blood; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D012016:Reference Values; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D004967:Estrogens; D009590:Nitrogen Radioisotopes; D019275:Radiopharmaceuticals; D009569:Nitric Oxide; D000641:Ammonia; D009638:Norepinephrine