Author + information
- Received February 28, 1994
- Revision received June 16, 1994
- Accepted June 30, 1994
- Published online December 1, 1994.
- J.Koudy Williams, DVM∗,
- Erika K. Honoré, DVM, MPH,
- Scott A. Washburn, MD and
- Thomas B. Clarkson, DVM
- ↵∗Address for correspondence: Dr. J. Koudy Williams, Department of Comparative Medicine, Bowman Gray School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1040.
Objectives. 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 (10−6mol/liter per min) and nitroglycerin (15 μg/min).
Results. Coronary arteries constricted during no hormone treatment (−8 ± 3% [mean ± SEMJ), 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 continue as MPA to the conjugated equine estrogen regimen diminished endothelium-mediated dilation.
☆ This study was supported in part by Grant P01-HL45666 and Contract HV53029 from the National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
- Received February 28, 1994.
- Revision received June 16, 1994.
- Accepted June 30, 1994.