Coadministration of nomegestrol acetate does not diminish the beneficial effects of estradiol on coronary artery dilator responses in nonhuman primates (Macaca fascicularis), , ,

Objective: Our purpose was to examine the effect of coadministered nomegestrol acetate on estradiol-induced dilator responses of coronary arteries. Study Design: In this prospective randomized trial, ovariectomized monkeys were fed a moderately atherogenic diet for 3 months while being treated with (1) no hormone replacement (control, n = 12), (2) estradiol (1.5 mg/d equivalent) added to the diet (n = 12), or (3) estradiol (1.5 mg/d equivalent) plus nomegestrol acetate (3.75 mg/d equivalent) (n = 12) added to the diet. Effects of treatment were measured with analysis of variance. Post hoc analyses were done by multiple comparison tests with Bonferroni corrections. Results: Constrictor responses of epicardial coronary arteries (measured with quantitative angiography) and decreased coronary blood velocity (measured with Doppler ultrasonography) to acetylcholine (10-6 mol/L) were less in the estradiol-treated monkeys (with or without cotreatment with nomegestrol acetate) than in the untreated monkeys (P< .05). Typical estrogenic responses were induced by estradiol in the endometrium (ie, increased proliferation [Ki-67 expression] [P<.04] and increased hormone receptor expression). These effects were antagonized by nomegestrol acetate. Conclusions: Although nomegestrol acetate has typical progestin-like effects on the uterus, it does not diminish the beneficial effects of estrogen on acetylcholine-induced dilator responses of coronary arteries. (Am J Obstet Gynecol 1998;179:1288-94.)