Dose-Response Effects of 2-Methoxyestradiol on Estrogen Target Tissues in the Ovariectomized Rat

• Published in: Endocrinology (Philadelphia) 2003-03, Vol.144 (3), p.785-792
• Main Authors: Sibonga, J. D, Lotinun, S, Evans, G. L, Pribluda, V. S, Green, S. J, Turner, R. T
• Format: Article
• Language: English
• Subjects: Aging; Animals; Biological and medical sciences; Body height; Body weight; Body Weight - drug effects; Body weight gain; Bone and Bones - drug effects; Bone Development - drug effects; Bone growth; Bone loss; Bone mass; Cancellous bone; Cholesterol; Cholesterol - blood; Dose-response effects; Dose-Response Relationship, Drug; Epithelial cells; Epithelium; Estradiol - administration & dosage; Estradiol - analogs & derivatives; Estrogen receptors; Estrogens; Estrogens - pharmacology; Ethinyl Estradiol - pharmacology; Experiments; Female; Fundamental and applied biological sciences. Psychology; Hormone replacement therapy; Metaphysis; Osteogenesis; Osteoporosis - prevention & control; Ovariectomy; Post-menopause; Rats; Receptors, Estrogen - drug effects; Receptors, Estrogen - physiology; Tumor suppression; Uterus; Uterus - drug effects; Weaning
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2002-220632

In three experiments, we evaluated the pharmacological effects of 2-methoxyestradiol (2ME2) on several estrogen target tissues. Experiment 1: we gavaged recently ovariectomized (OVX) 9.5-wk-old rats with 2ME2 at doses of 0, 0.1, 1, 4, 20, and 75 mg/kg in a 21-d dose-response study. 2ME2 reduced body weight and serum cholesterol, increased uterine weight and epithelial cell height, and inhibited longitudinal and radial bone growth compared with values in the untreated OVX rat. All doses of 2ME2 maintained cancellous bone mass at the baseline level, the lowest effective dose being 20-fold less than a uterotrophic dose. Experiment 2: in an 8-wk experiment in adult OVX rats, a nonuterotrophic dose of 2ME2 (4 mg/kg·d) suppressed body weight gain, inhibited bone formation in cancellous bone and partially prevented bone loss in the tibial metaphysis. Experiment 3: in weanling rats, ICI 182,780 did not antagonize the effect of 2ME2. We conclude that 2ME2 antagonizes the skeletal changes that follow OVX at doses that have minimal or no effects in the uterus in both young and adult rats; 2ME2 does not appear to act via estrogen receptors and is active on bone at doses well below those required for tumor suppression in mice. 2ME2, through a novel pathway, may be a useful alternative to conventional hormone replacement therapy for prevention of postmenopausal bone loss.