Estrogen-induced increases in coronary blood flow are antagonized by inhibitors of nitric oxide synthesis.
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.
Lang
U
U
Zentrum für Geburtshilfe und Frauenheilkunde am Klinikum, Justus-Liebig-Universität Giessen, Germany.
Baker
R S
RS
Clark
K E
KE
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
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D004958:Estradiol; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester