Involvement of androgen receptor in 17beta-estradiol-induced cell proliferation in rat uterus.
Although it is known that, in the uterus, estrogen receptor alpha (ERalpha) is involved in proliferation and progesterone receptor in differentiation, the role of the two other gonadal-hormone receptors expressed in the uterus, androgen receptor (AR) and estrogen receptor beta (ERbeta), remains undefined. In this study, the involvement of AR in 17beta-estradiol (E(2))-induced cellular proliferation in the immature rat uterus was investigated. AR levels were low in the untreated immature uterus, but 24 h after treatment of rats with E(2), there was an increase in the levels of AR and of two androgen-regulated genes, IGF-I and Crisp (cysteine-rich secretory protein). As expected, E(2) induced proliferation of luminal epithelial cells. These actions of E(2) were all blocked by both the antiestrogen tamoxifen and the antiandrogen flutamide. The E(2)-induced AR was found by immunohistochemistry to be localized exclusively in the stroma, mainly in the myometrium, where it colocalized with ERalpha but not with ERbeta. ERbeta, detected with two different ERbeta-specific antibodies, was expressed in both stromal and epithelial cells either alone or together with ERalpha. Treatment with E(2) caused down-regulation of ERalpha and ERbeta in the epithelium. The data suggest that, in E(2)-induced epithelial cell proliferation, ERalpha induces stromal AR and AR amplifies the ERalpha signal by induction of IGF-I. Because AR is never expressed in cells with ERbeta, it is unlikely that ERbeta signaling is involved in this pathway. These results indicate an important role for AR in proliferation of the uterus, where estrogen and androgen do not represent separate pathways but are sequential steps in one pathway.
Departments of Medical Nutrition and Bioscience, Karolinska Institute, Novum, Huddinge, Stockholm S-141 86, Sweden. zhang.weihua@mednut.ki.se
Zhang
Z
Weihua
Jenny
J
Ekman
Asa
A
Almkvist
Shigehira
S
Saji
Ling
L
Wang
Margaret
M
Warner
Jan-Ake
JA
Gustafsson
D000726:Androgen Antagonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005260:Female; D005485:Flutamide / Q000494:pharmacology; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011944:Receptors, Androgen / Q000096:biosynthesis / Q000502:physiology*; D011960:Receptors, Estrogen / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013629:Tamoxifen / Q000494:pharmacology; D014599:Uterus / Q000166:cytology* / Q000187:drug effects
D000726:Androgen Antagonists; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013629:Tamoxifen; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D005485:Flutamide