title: Estrogens reduce bone loss in the ovariectomized, lactating rat model.
abstract: Estrogen treatment of ovariectomized, lactating rats improved retention of bone mineral mass by 15-25% compared to ovariectomized, lactating rats receiving vehicle only. On the second day postpartum all lactating rats were ovariectomized and were placed along with age-matched non-mated controls on a whole-wheat flour-based diet with 0.1% calcium and 0.4% phosphorus. On day 6 postpartum estrogen treatment was begun with either implantation of a slow-release 17 beta-estradiol pellet or with the first of daily subcutaneous injections in sesame oil (vehicle). Increasing doses of estrogen resulted in decreased food consumption and decreased litter weight gain, both well-known effects of estrogens. Ovariectomized, lactating rats implanted with a slow-release pellet containing 0.35 mg 17 beta-estradiol had mean serum estradiol levels of 113.5 pg/ml. At the end of 21 days of lactation, femurs of dams with placebo pellets showed loss of 54% of bone ash weight compared with the non-mated controls versus only 42% loss by rats receiving estradiol treatment. Rats were also injected with estradiol benzoate in a sesame oil vehicle at 3 dose levels of 1.6, 5, or 16 micrograms/day. Only the 5 and 16 micrograms/day doses significantly improved retention of bone mineral mass during lactation (+17% and +18%, respectively, vs vehicle-injected, lactating rats). Estrone administered by subcutaneous injection also improved retention of bone during lactation; however, injection of 50 micrograms/day of estrone was required to produce an equivalent bone retention compared to 5 micrograms/day of estradiol. Thus, treatment of ovariectomized, lactating rats with estrogens results in a significant reduction of the loss of bone mineral mass associated with lactation.
authors.affiliation: Department of Nutrition, School of Public Health, University of North Carolina, Chapel Hill 27599-7400.
authors.forename: S C
authors.initials: SC
authors.lastname: Garner
authors.forename: J J
authors.initials: JJ
authors.lastname: Anderson
authors.forename: M H
authors.initials: MH
authors.lastname: Mar
authors.forename: I
authors.initials: I
authors.lastname: Parikh
mesh_terms: D000818:Animals; D015519:Bone Density / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000097:blood; D003692:Delayed-Action Preparations; D004195:Disease Models, Animal; D004435:Eating / Q000187:drug effects; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D005260:Female; D007774:Lactation; D009929:Organ Size / Q000187:drug effects; D010024:Osteoporosis / Q000517:prevention & control*; D010052:Ovariectomy; D010758:Phosphorus / Q000097:blood; D011247:Pregnancy; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D003692:Delayed-Action Preparations; D010758:Phosphorus; D004958:Estradiol; D002118:Calcium