title: Estrogen dose required to maintain parathyroid hormone mediated bone gain in osteopenic ovariectomized rats is probably higher than in preventive treatment with estrogen.
abstract: Successful prevention of bone loss in ovariectomized rats with 17 beta-estradiol (E2) at 10 micrograms/kg/d has been reported. Here we show that E2 dose twice that much is not enough to maintain PTH(1-34) mediated bone gain. Three-month-old female Wistar rats were ovariectomized and fed with regular rodent chow and water ad libitum. Three months later they were divided into 9 groups (5-8 per group) and treated cyclically with PTH(1-34) (20 micrograms/kg/d sc, 5d/w for 3w) and E2 (20 micrograms/kg/d sc, 5d/w for 4w). There were also a baseline group and five vehicle control groups. Cancellous bone volume (Cn.BV/TV) of distal femoral metaphyses was measured by computer-aided histomorphometry on trichrome stained thin sections, and 24-hour fasted urine was analyzed for pyridinoline/creatinine (PYR/CREA) by immunoassay. Histomorphometric results showed that PTH(1-34) progressively increased Cn.BV/TV but E2 failed to maintain them. Urinary PYR/CREA results showed that E2-treated groups had lower values. We conclude that E2 dose > 20 micrograms/kg/d is required to maintain the PTH mediated bone gain.
authors.affiliation: Department of Pathology, Mount Sinai Hospital, University of Toronto, Canada.
authors.forename: P T
authors.initials: PT
authors.lastname: Cheng
authors.forename: L M
authors.initials: LM
authors.lastname: Aye
authors.forename: R
authors.initials: R
authors.lastname: Vieth
authors.forename: K
authors.initials: K
authors.lastname: Müller
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001851:Bone Diseases, Metabolic / Q000188:drug therapy* / Q000209:etiology / Q000517:prevention & control; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D010281:Parathyroid Hormone / Q000627:therapeutic use*; D010446:Peptide Fragments / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D019379:Teriparatide; D015430:Weight Gain / Q000187:drug effects
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D019379:Teriparatide; D004958:Estradiol