Evaluation of in vivo estrogenic potency of natural estrogen-active chemical, puerarin, on pituitary function in gonadectomized female rats.
OBJECTIVE
Previous research has revealed that puerarin, the major phytoestrogen in tuberous roots of Pueraria lobata and Pueraria mirifica, acts as a selective estrogen receptor modulator that displays predominantly estrogenic potential for health benefit. However, little is known about the estrogenic potency of puerarin in pituitary, especially in the rat model of postmenopausal females.


METHODS
Plasma prolactin and growth hormone levels as well as mRNA expression levels of pituitary estrogen-regulated genes, such as estrogen receptor (ER) subtypes alpha (ERα) and beta (ERβ), truncated ER product-1 (TERP-1) and -2 (TERP-2) and gonadotropin alpha subunit, were examined using radioimmunoassay and TaqMan® real-time PCR, respectively. The effects were compared with the potent ER agonist, 17β-estradiol-3-benzoate (E2B), and both substances were supplemented at low and high doses, i.e., 0.6 or 3g puerarin and 0.0043 or 0.0173g E2B per kilogram of phytoestrogens-free rat chow, and applied to ovariectomized rats (five groups; 11-12 rats per group) for 12weeks.


RESULTS
Puerarin possessed weak E2B-like activities on pituitary function by acting as ERβ and TERP-1/-2 agonists, which resulted in the downregulation and upregulation of ERβ and TERP-1/-2 mRNA expressions, respectively, and elevation of growth hormone levels. There were trends of decreased levels of alpha subunit mRNA transcripts and increased levels of prolactin in puerarin-treated rats as observed in E2B-treated animals.


CONCLUSIONS
This is the first report in ovariectomized rats the effects of puerarin on somatotropes and pituitary estrogen-responsive mRNA expressions, which are very weakly estrogenic by acting through ERβ- and TERP-1/-2 mediated pathways.
Department of Biology, Faculty of Science, Mahasarakham University, Khamriang Sub-district, Kantharawichai District, Mahasarakham Province 44150, Thailand. Electronic address: oupanida@hotmail.com.
Panida
P
Loutchanwoot
Department of Endocrinology, Faculty of Medicine, University Medical Center Göttingen, Robert-Koch-Strasse 40, D-37075 Göttingen, Germany.
Tina
T
Vortherms
Department of Endocrinology, Faculty of Medicine, University Medical Center Göttingen, Robert-Koch-Strasse 40, D-37075 Göttingen, Germany.
Hubertus
H
Jarry
D000818:Animals; D047628:Estrogen Receptor alpha / Q000235:genetics; D047629:Estrogen Receptor beta / Q000235:genetics; D005260:Female; D066298:In Vitro Techniques; D007529:Isoflavones / Q000494:pharmacology*; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects* / Q000502:physiology; D010907:Pituitary Hormones / Q000097:blood* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D007529:Isoflavones; D010907:Pituitary Hormones; D012333:RNA, Messenger; C033607:puerarin
17β-estradiol-3-benzoate (PubChem CID: 222757); Estradiol; Estrogen receptors; Growth hormone; Pituitary; Prolactin; Puerarin; Puerarin (PubChem CID: 5281807); Somatotrope; Truncated estrogen receptor products; mRNA expression