title: 17 beta-estradiol stimulates cancellous bone formation in female rats.
abstract: Estrogen is generally considered to maintain bone mass through suppression of bone resorption. We have previously demonstrated that administration of pharmacological doses of estrogen increases bone formation in rats. Because such high doses of estrogen might induce bone formation through some mechanism other than the estrogen receptor, we have now assessed the effect of more physiological doses of 17 beta-estradiol (E2) on bone formation. Adult female rats (13 weeks and 6 months old) administered E2 (1, 4, 40, 400, and 4 mg/kg daily for 17-21 days) showed a dramatic increase (5- to 8-fold) in cancellous bone formation, attributable to a combination of an increase in the proportion of bone surface actively undertaking bone formation, and an increase in the rate of mineral apposition. Significant anabolism was induced in 6-month-old rats by doses as low as 4 micrograms/kg and in 13-week-old rats by 40 micrograms/kg. Corresponding increases in the proportion of trabecular surface covered by osteoblasts were also observed. Histomorphometric indices of bone resorption were suppressed by estrogen. Estrogen administration caused an increase in bone volume up to 35% over controls, over a 21-day period. Stimulation of bone formation by estrogen showed a similar pattern of dose-responsiveness to recognized physiological targets of E2: suppression of longitudinal growth and uterine growth. These results suggest that stimulation of cancellous bone formation is a physiological action of E2 in the rat.
authors.affiliation: Department of Histopathology, St. George's Hospital Medical School, London, United Kingdom.
authors.forename: J W
authors.initials: JW
authors.lastname: Chow
authors.forename: J M
authors.initials: JM
authors.lastname: Lean
authors.forename: T J
authors.initials: TJ
authors.lastname: Chambers
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D001846:Bone Development / Q000187:drug effects*; D001862:Bone Resorption; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D005260:Female; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D014599:Uterus / Q000187:drug effects* / Q000502:physiology
chemical_list: D004958:Estradiol