Estrogen receptor subtype-specific effects on markers of bone homeostasis.
To further elucidate the processes involved in the physiology of bone-protection by estrogens, ovariectomized (OVX) rats were treated subcutaneously with 17beta-estradiol (E(2)), the ERalpha-specific agonist (16alpha-LE2) and the ERbeta-specific agonist (8beta-VE2). OVX and intact animals served as controls. Biomarkers of bone-formation (osteocalcin (OC), osteopontin (OPN)) and bone-resorption (telopeptides of collagen type I (CTx), pyridinoline cross-links (Pyd)) were quantified. Bone mineral density was measured by computed tomography. OVX-induced bone loss could be antagonized by subcutaneous administration of 17beta-estradiol and 16alpha-LE2. Serum levels of CTx, OC and OPN were significantly elevated in OVX compared to intact animals and reduced by 17beta-estradiol and 16alpha-LE2. Treatment of OVX rats with 8beta-VE2 did not affect bone mineral density (BMD) or bone-marker serum levels. Taken together, the complex expression pattern of bone-markers in OVX rats following subcutaneous administration of ER subtype-specific agonists indicates that 17beta-estradiol exerts its bone-protective effects by modulating the activity of osteoclasts and osteoblasts via ERalpha.
Hertrampf
T
T
Institut für Kreislaufforschung und Sportmedizin, Abt. molekulare und zelluläre Sportmedizin, DSHS Köln, Germany. hertrampf@dshs-koeln.de
Schleipen
B
B
Velders
M
M
Laudenbach
U
U
Fritzemeier
K H
KH
Diel
P
P
D000818:Animals; D015415:Biomarkers / Q000378:metabolism*; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006706:Homeostasis; D015394:Molecular Structure; D009929:Organ Size; D010052:Ovariectomy; D011897:Random Allocation; D051381:Rats; D014599:Uterus / Q000033:anatomy & histology / Q000378:metabolism
D015415:Biomarkers; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004958:Estradiol