Estrogen induces insulin-like growth factor-I expression in the rat uterus.
The inability to convincingly demonstrate a mitogenic effect of estrogen on isolated uterine cells in culture suggests that autocrine or paracrine growth factors may be important in the estrogen-induced uterine proliferative response. Here we report that uterine expression of insulin-like growth factor-I (IGF-I), an important mediator of GH action, is increased after 17 beta-estradiol (5 micrograms/100 g bw, ip) administration to ovariectomized prepubertal rats. An increase in uterine IGF-I mRNA abundance, approximately 14-fold above untreated controls, was apparent 6 h after estrogen administration and the level achieved exceeded that seen in the uterus from intact mature rats during diestrus. In contrast to the increase in IGF-I expression in the uterus, no significant change in serum IGF-I concentration or hepatic or renal IGF-I mRNA abundance was demonstrable after 17 beta-estradiol injection of ovariectomized prepubertal rats. The increase in uterine IGF-I expression, was similar in both pituitary-intact and hypophysectomized, ovariectomized rats. We believe this is the first report of induction of IGF-I expression by estrogen in vivo. As such, the finding expands the role and significance of IGF-I as a mediator of growth beyond that related to GH.
Murphy
L J
LJ
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Murphy
L C
LC
Friesen
H G
HG
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology; D007016:Hypophysectomy; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology; D010902:Pituitary Gland / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism
D004958:Estradiol; D012313:RNA; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone