Effects of hormone replacement therapy on reactivity of atherosclerotic coronary arteries in cynomolgus monkeys.
OBJECTIVE
We attempted to determine whether continuous and cyclic medroxyprogesterone acetate modulates the effects of estrogen on dilation of atherosclerotic coronary arteries in surgically postmenopausal female monkeys.


BACKGROUND
Estrogen replacement in postmenopausal women preserves normal dilator responses of atherosclerotic coronary arteries. The effects of progestins on coronary artery reactivity have not been determined.


METHODS
Repeated quantitative coronary angiography was used to study the effects after 1 month of 1) no hormone replacement (control) or oral administration of 2) continuous conjugated equine estrogens, 3) cyclic high dose medroxyprogesterone acetate (MPA) given on days 16 to 26 of the month, 4) conjugated equine estrogens plus continuous low dose MPA, or 5) conjugated equine estrogens plus cyclic high dose MPA on endothelium-mediated dilation of atherosclerotic coronary arteries in 12 cynomolgus monkeys. Change in diameter of the left circumflex coronary artery was measured in response to intracoronary infusions of acetylcholine (10(-6) mol/liter per min) and nitroglycerin (15 micrograms/min).


RESULTS
Coronary arteries constricted during no hormone treatment (-8 +/- 3% [mean +/- SEM]), dilated during conjugated equine estrogen treatment (+3 +/- 1%, p < 0.05 vs. control) and constricted during cyclic MPA treatment (-3 +/- 2%). Addition of cyclic or continuous MPA to the conjugated equine estrogen regimen inhibited acetylcholine responses by 50% (p < 0.05 vs. conjugated equine estrogens). There was no effect of treatment on vascular response to nitroglycerin (p > 0.05).


CONCLUSIONS
Treatment with conjugated equine estrogens, but not MPA, augmented endothelium-mediated dilation of atherosclerotic coronary arteries. Addition of cyclic or continuous MPA to the conjugated equine estrogen regimen diminished endothelium-mediated dilation.
Comparative Medicine Clinical Research Center, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27157-1040.
J K
JK
Williams
E K
EK
Honoré
S A
SA
Washburn
T B
TB
Clarkson
D000818:Animals; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000188:drug therapy / Q000503:physiopathology*; D003331:Coronary Vessels / Q000187:drug effects / Q000503:physiopathology; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D008252:Macaca fascicularis; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects*
D004967:Estrogens; D017258:Medroxyprogesterone Acetate