Estrogen regulation of the estrogen receptor and insulinlike growth factor-I in the rat uterus: a potential coupling between effects of estrogen and IGF-I.
The interrelationship between estrogen and insulin-like growth factor-I (IGF-I) in the regulation of uterine growth was studied in the rat. The levels of the estrogen receptor (ER), ER mRNA, and IGF-I mRNA in rat uterus and liver were monitored. Uterine ER in normal cycling rats was highest in proestrus and diestrus, as was IGF-I mRNA. ER mRNA and plasma estradiol peaked in proestrus. Hepatic ER mRNA and IGF-I mRNA were highest in diestrus, whereas ER was not significantly changed during the estrous cycle. The temporal effects of multiple injections or continuous infusion of 17 beta-estradiol in ovariectomized rats were examined. In the uterus of animals subjected to multiple injections, a 10-fold increase in IGF-I mRNA was seen 24 h after the start of the treatment, whereas rats given continuous infusion of estradiol showed a more than 16-fold increase. In both groups, the increase of IGF-I mRNA was transient although estrogen treatment was continued. To study local hormonal effects, ovariectomized rats were given estradiol in vaginal implants. The uterine IGF-I mRNA level increased two-fold in 3 days. The ER mRNA level increased 1.5-fold and the uterine weights were doubled. The plasma estradiol concentration did not change during the treatment. A separate experiment was carried out to establish whether IGF-I itself exercises estrogen-like effects. Ovariectomized rats were given hrIGF-I in osmotic minipumps for 3 days. The uteri of the treated animals weighted significantly more than did the controls. Quantitation of the level of uterine estrogen receptors revealed a significant decrease.(ABSTRACT TRUNCATED AT 250 WORDS)
Sahlin
L
L
Division for Reproductive Endocrinology, Karolinska Hospital, Stockholm, Sweden.
Norstedt
G
G
Eriksson
H
H
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000502:physiology; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000187:drug effects* / Q000235:genetics; D012015:Reference Standards; D012016:Reference Values; D014599:Uterus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
D012333:RNA, Messenger; D011960:Receptors, Estrogen; D004958:Estradiol; D007334:Insulin-Like Growth Factor I