The effect of ovariectomy and ovarian steroid treatment on growth hormone and insulin-like growth factor-I levels in the rat femur.
Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are known to play an important role in bone metabolism. The regulation of plasma levels of GH and IGF-I by ovarian steroids is well known, however, their effect on local GH and IGF-I is still unclear. In this study, we investigated the effect of ovariectomy and ovarian steroid treatment on the femur GH and IGF-I levels as well as on bone density in the rat. Nine month-old rats were ovariectomized (OVX) or sham-operated (SHAM) and 9 weeks after the surgery they were treated with daily s.c. injections of either 17beta-estradiol (OVX + E), progesterone (OVX + P), or vehicle (OVX + V) for another 10 weeks. GH and IGF-I levels in the femur extracts were measured by specific radioimmunoassay (RIA). Ovariectomy decreased GH and had no effect on IGF-I levels. Estradiol treatment increased femur GH and IGF-I levels compared to SHAM rats. Progesterone restored GH and increased IGF-I levels. Ovariectomy decreased, estrogen restored and progesterone partially restored femur bone density. Our results demonstrate that ovariectomy and ovarian steroids modulate the levels of GH and IGF-I in the bone of aged OVX rats. However, these effects appear to be limited to supraphysiological concentrations of estradiol and progesterone.
Suliman
I A
IA
Department of Orthopedic Surgery, Karolinska Institute, Huddinge University Hospital, Stockholm, Sweden. isam_suliman@hotmail.com
El-Bakri
N K
NK
Adem
A
A
Mustafa
A
A
Lindgren
J U
JU
D000818:Animals; D015519:Bone Density; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005269:Femur / Q000737:chemistry* / Q000187:drug effects; D013006:Growth Hormone / Q000032:analysis*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone