Stimulation of trabecular bone formation by insulin-like growth factor I in adult ovariectomized rats.
Although in vitro experiments indicate that insulin-like growth factor I (IGF-I) is an anabolic hormone in bone cell metabolism, the effects of IGF-I in vivo on bone formation are unclear. We thus investigated whether IGF-I is able to stimulate bone formation in adult rats with established osteopenia induced by ovariectomy (OVX). IGF-I was administered at daily doses of 0.05, 0.2, and 0.8 mg/kg for 3 wk. OVX induced a marked osteopenia in femur and tibia. Administration of IGF-I increased trabecular bone mass with a maximal effect at 0.2 mg/kg. The same dose stimulated bone formation, as revealed by an increase in osteoid surface, osteoblast surface, triple tetracycline-labeled surface, and bone formation rate. The mineral apposition rate was equally stimulated at all doses. At the highest dose, IGF-I increased osteoclast surface and osteoclast number. These data indicate that, in the adult OVX rat, IGF-I stimulates bone formation and increases trabecular bone volume at medium doses and enhances the histological indexes of bone resorption at high doses.
Mueller
K
K
Research Department, Ciba-Geigy, Basel, Switzerland.
Cortesi
R
R
Modrowski
D
D
Marie
P J
PJ
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001851:Bone Diseases, Metabolic / Q000503:physiopathology*; D001852:Bone Lengthening; D001862:Bone Resorption / Q000503:physiopathology; D001842:Bone and Bones / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009929:Organ Size / Q000187:drug effects; D010012:Osteogenesis / Q000187:drug effects*; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014599:Uterus / Q000033:anatomy & histology; D015430:Weight Gain / Q000187:drug effects
D007334:Insulin-Like Growth Factor I; D000469:Alkaline Phosphatase